Yo, en cambio, pedí un batido frío con pajita y me senté junto a la ventana.

Yes—Spanish often drops subject pronouns because the verb ending already shows who is doing the action. In pedí and me senté, the -í and -é endings already tell you the subject is I.

Here, yo is used for emphasis or contrast. That fits especially well with en cambio:

Yo, en cambio, ... = I, on the other hand, ...

So yo is not required grammatically, but it sounds natural when the speaker is contrasting their actions with someone else’s.

En cambio means on the other hand, by contrast, or instead depending on context.

It introduces a contrast with something mentioned before. In this sentence, it signals that what I did was different from what someone else did.

It is often set off with commas when it works like a parenthetical expression:

Yo, en cambio, pedí...

That punctuation helps show it is a discourse marker rather than part of the main clause.

Pedí is the preterite, used for a completed action in the past:

pedí = I ordered / I asked for

In this sentence, the speaker is telling a sequence of finished actions:

• pedí a cold milkshake
• me senté by the window

That is why the preterite fits well.

Pedía is the imperfect, which would suggest something more habitual, ongoing, descriptive, or backgrounded:

• pedía un batido frío = I used to order / I was ordering a cold milkshake

So pedí is the natural choice for a one-time completed event in a story.

Yes, but only partly.

Pedir is a stem-changing verb, and in the preterite it changes e → i only in the third person forms:

• yo pedí
• tú pediste
• él/ella pidió
• nosotros pedimos
• vosotros pedisteis
• ellos/ellas pidieron

So in pedí, there is no stem change. The irregularity shows up in forms like pidió and pidieron.

The accent marks show where the stress falls.

• pedí is stressed on the last syllable: pe-DÍ
• senté is stressed on the last syllable: sen-TÉ

They also help distinguish these forms visually from other possible forms and make the pronunciation clear.

In regular preterite forms of -ar and -ir verbs, the yo form often has a written accent:

• hablé
• compré
• viví
• pedí

In Spanish, adjectives usually come after the noun.

So:

• un batido frío = a cold milkshake

That is the normal order for a straightforward, literal description such as temperature.

If an adjective goes before the noun in Spanish, it often adds a more subjective, literary, or emphatic nuance. With frío, the normal and expected order here is after the noun.

In Spain, pajita means drinking straw.

So: con pajita = with a straw

This is a very Spain-specific everyday word. In other Spanish-speaking countries, other words are common, such as:

• popote
• pitillo
• pajilla
• sorbete

But in Spain, pajita is the usual word.

Because the verb here is sentarse, which means to sit down.

• me senté = I sat down

Without the pronoun, sentar is usually a different verb:

• sentar a alguien = to seat someone
• Esta camisa me sienta bien = This shirt suits me

So:

• me senté = I sat down myself
• senté a mi hijo = I seated my son

That is why the reflexive pronoun me is necessary here.

For the same reason as pedí: it describes a completed action in a sequence of events.

The speaker is narrating what happened:

1. I ordered
2. I sat down

So the preterite is the natural tense.

If you said me sentaba, it would usually mean something like:

• I used to sit down
• I was sitting down depending on context

That would not match this neat sequence of finished actions as well.

Junto a means next to, beside, or by.

So: junto a la ventana = by / next to the window

It usually suggests closer physical position than cerca de, which means near.

Compare:

• junto a la ventana = right by the window
• cerca de la ventana = near the window

Both are possible in some contexts, but junto a gives a stronger sense of being directly beside it.

La ventana uses the definite article because it refers to a window understood as identifiable in the situation—probably the window in that café, restaurant, or room that both speaker and listener can imagine.

Spanish often uses the definite article in places where English also would, or where English might be slightly looser depending on context.

If you said una ventana, it would sound more like:

• some window, not a specific one
• one of several possible windows

In this sentence, la ventana sounds more natural because it feels like a concrete, known location in the scene.

It describes the drink.

So the structure is understood as:

pedí [un batido frío con pajita]

That means:

• a cold milkshake with a straw

It does not mean that the speaker did the ordering using a straw. Spanish, like English, places this kind of phrase where it naturally attaches to the noun phrase.

Because en cambio is being used as a parenthetical contrast marker, not as a core part of the clause structure.

So the commas show a pause:

Yo, en cambio, pedí...

This is similar to English punctuation in phrases like:

• I, on the other hand, ordered...

Without commas, the sentence would be less natural and harder to read.