Learn Hardcore Spanish (Latin America): Pintamos un cartel político en la manifestación pacífica. - We paint a political sign at the peaceful protest.

Which one it is depends on context.
In the sentence Pintamos un cartel político en la manifestación pacífica, speakers will usually understand it as past (“we painted…”) unless the wider context clearly refers to a habitual action or something happening right now.

If you want to make the past 100% clear, you can add a time word:

Ayer pintamos un cartel político… – Yesterday we painted a political sign…

If you want to make the present 100% clear:

Ahora pintamos un cartel político… – Now we’re painting a political sign…

Why is there no word for “we” in the sentence?

Spanish often drops the subject pronoun (like yo, tú, nosotros) because the verb ending already shows the subject.

Pintamos already tells you “we paint / painted”.
So nosotros is usually optional:
- Pintamos un cartel político…
- Nosotros pintamos un cartel político… (more emphasis on “we”)

You normally only add nosotros to:

Emphasize contrast: Nosotros pintamos el cartel, no ellos. – We painted the sign, not them.
Avoid ambiguity if several groups of people are being talked about.

In everyday speech, leaving it out is completely natural.

Why is it un cartel político and not una cartel política?

Because cartel is masculine in Spanish.

el cartel – the sign / poster
un cartel – a sign / poster

Adjectives must agree in gender and number with the noun they describe.
So:

Masculine singular: un cartel político
Feminine singular: una pancarta política (here pancarta is feminine)
Plural masculine: unos carteles políticos
Plural feminine: unas pancartas políticas

Using una cartel or cartel política would be grammatically incorrect, because the article and adjective would not match the noun’s gender.

Does cartel mean “drug cartel” in Spanish? Why is it used for “sign/poster”?

Yes, cartel has two common meanings:

Sign / poster
- Pintamos un cartel político. – We painted a political sign/poster.
- Hay carteles en la calle. – There are posters/signs in the street.
Cartel in the economic/criminal sense (including “drug cartel”)
- Un cartel de la droga – a drug cartel

Usually, the meaning is clear from context:

If the verb is pintar and you’re at a demonstration, cartel = poster/sign.
If you mention drug trafficking, crime, or business agreements, cartel = cartel (organization).

So in your sentence, nobody will think of a drug cartel; they’ll understand it as a poster/sign.

In Latin American Spanish, could I say póster, afiche, or pancarta instead of cartel?

Yes, but there are regional and nuance differences:

cartel – widely understood; can be a poster, sign, or notice.
póster – very common for posters (often decorative, like band/movie posters).
afiche – common in parts of Latin America (e.g. Argentina, Uruguay, Peru) for advertising/poster.
pancarta – usually a big sign/banner used specifically at protests, marches, demonstrations.

For a protest, many Latin Americans would find pancarta especially natural:

Pintamos una pancarta política en la manifestación pacífica.

But cartel is still correct and understandable everywhere.

Why is político placed after cartel? Could I put it before, like in English “political poster”?

In Spanish, adjectives normally come after the noun:

un cartel político – a political poster
una manifestación pacífica – a peaceful demonstration

Putting político before the noun (un político cartel) would sound wrong or change the structure in an unnatural way. You generally don’t use político before cartel in this sense.

There are some adjectives that can go before the noun (like buen, gran, nuevo) and sometimes change meaning depending on the position, but político is not one of these flexible adjectives in this context.

So:

✅ un cartel político
❌ un político cartel (not used with this meaning)

Could cartel político also mean “political cartel” (like a group of politicians)?

On its own, cartel político would usually be understood as “political poster/sign”, especially with a verb like pintar.

To talk about an organization/group, Spanish typically uses different structures, for example:

un cartel de políticos – a cartel of politicians (sounds like a corrupt group)
un grupo político – a political group
una organización política – a political organization

So, in your sentence:

Pintamos un cartel político… clearly refers to an object (a poster), not a group.

Why is it la manifestación and not una manifestación?

The definite article la (the) is used because we are referring to a specific demonstration that both speaker and listener know about:

la manifestación pacífica – the peaceful demonstration (a particular one)

If you said una manifestación pacífica, it would sound like any or some peaceful demonstration, not a specific one:

Pintamos un cartel político en una manifestación pacífica.
= We painted a political sign at a peaceful demonstration (not specified which).

Using la often suggests:

The demonstration was already mentioned earlier in the conversation, or
It’s clear from context which one you mean (e.g. “the big one that happened yesterday in the city center”).

What’s the difference between manifestación, protesta, and marcha?

All three are related but have slightly different focuses:

manifestación
A demonstration/rally where people gather, usually in public, to express an opinion.
Can include speeches, signs, chanting, marching.
- Vamos a la manifestación contra la corrupción.
protesta
More general: protest as an act of expressing disagreement or discontent.
It can be in the street, online, at work, etc.
- Hubo una protesta frente al edificio del gobierno.
marcha
Literally a march: people moving/walking together along a route for a cause.
- Participamos en una marcha por los derechos humanos.

In your sentence, manifestación emphasizes the public demonstration event where people are gathered, and that’s a very natural word in this context.

Why is it pacífica and not pacífico?

Because pacífica is an adjective that must agree with the noun it describes.

manifestación is feminine singular: la manifestación
So the adjective must also be feminine singular: pacífica

Agreement:

Feminine singular: una manifestación pacífica
Masculine singular: un acto pacífico
Feminine plural: unas manifestaciones pacíficas
Masculine plural: unos actos pacíficos

If you used pacífico here (la manifestación pacífico), it would be grammatically incorrect because pacífico is masculine while manifestación is feminine.

Note: Nouns ending in -ción (like manifestación, nación, organización) are almost always feminine.

Why is the preposition en used? Could I say durante la manifestación or a la manifestación instead?

En is used to express location: “in/at the peaceful demonstration.”

Pintamos un cartel político en la manifestación…
= We painted the sign at the demonstration (while being there).

You can say durante la manifestación, but the nuance is slightly different:

durante la manifestación = during the demonstration (focus on time)
en la manifestación = at/in the demonstration (focus on place; you were there)

So:

Pintamos un cartel político durante la manifestación pacífica.
Highlights that the painting happened in that time frame.

A la manifestación would usually combine with verbs of movement:

Fuimos a la manifestación. – We went to the demonstration.
Llevamos un cartel a la manifestación. – We took a sign to the demonstration.

With pintar, en la manifestación is the most natural: you painted it there.

What do the accent marks in político, manifestación, and pacífica indicate?

The written accents (tildes) tell you where to stress the word and sometimes help distinguish words with different meanings.

político – stress on LÍ: po-LÍ-ti-co
Without the accent (politico) you would be forced (by spelling rules) to stress TI, which would be wrong.
manifestación – stress on CIÓN: mani-festa-CIÓN
Words ending in -ción always take the stress on that last syllable and always have a written accent.
pacífica – stress on CÍ: pa-CÍ-fi-ca
Without the accent (pacifica), the stress would fall on FI (pa-ci-FI-ca), which is a different word:
- pacífica (with accent): adjective = peaceful (feminine)
- pacifica (without accent): verb form of pacificar (he/she/it pacifies)

So the accents:

Show the correct pronunciation/stress.
Sometimes distinguish different words (like pacífica vs pacifica).