Cuando salimos con el perro de mi vecina, siempre llevamos la correa y una botella de agua.

Because cuando has no accent when it is used as a conjunction meaning when inside a sentence:

• Cuando salimos... = When we go out...

It takes an accent — cuándo — only in direct or indirect questions:

• ¿Cuándo salimos? = When are we leaving?
• No sé cuándo salimos. = I don't know when we’re leaving.

So here, since it introduces a time clause, cuando is correct.

Here salimos is present tense because the sentence describes a habitual action:

• Cuando salimos..., siempre llevamos...
• When we go out..., we always take...

Spanish often uses the present tense for repeated or general actions, just like English does in sentences such as When we go out, we always...

Also, salimos can sometimes also be a preterite form (we went out), but in this sentence siempre clearly shows it is the present habitual meaning.

Because Spanish usually omits subject pronouns when the verb form already makes the subject clear.

• salimos = we go out
• llevamos = we carry / we take

So Spanish does not need nosotros unless the speaker wants emphasis or contrast:

• Nosotros salimos con el perro, pero ellos no.
• We go out with the dog, but they don’t.

In a normal sentence, leaving it out sounds more natural.

Here salir con el perro means something like:

• to go out with the dog
• to take the dog out

Literally, salir means to go out / to leave, and con means with. In this context, it suggests going outside together with the dog, probably for a walk.

Be careful: salir con alguien can also mean to go out with someone in the sense of dating, but that meaning does not apply here because the context is clearly about a dog.

Spanish often expresses ideas a little differently from English.

English often says:

• take the dog out

Spanish can say:

• salir con el perro = go out with the dog
• sacar al perro = take the dog out

Both are possible, but they are slightly different in focus:

• salir con el perro focuses on you going out together with the dog
• sacar al perro focuses more directly on taking the dog outside

So this sentence is perfectly natural, just phrased in a more Spanish way.

De mi vecina means of my female neighbor or my female neighbor’s.

Spanish usually shows possession with de:

• el perro de mi vecina = my neighbor’s dog

The word vecina is feminine, so it means the neighbor is a woman. If it were a man, it would be:

• el perro de mi vecino

Spanish does not normally add an apostrophe like English (neighbor’s). It uses the de structure instead.

Spanish uses articles more often than English.

• el perro = the dog
• la correa = the lead / leash
• una botella de agua = a bottle of water

Here is the difference:

• el perro refers to a specific dog: the neighbor’s dog
• la correa refers to the relevant leash for that situation, so Spanish naturally uses the definite article
• una botella de agua means one / a bottle of water, introducing it as an item you bring

Spanish often uses the definite article where English might also say the, but sometimes Spanish sounds more article-heavy overall.

Yes. Correa can mean several related things depending on context, including:

• leash / lead
• strap
• belt

In this sentence, because it is about going out with a dog, la correa clearly means the leash or lead.

For Spain, correa is a normal word for a dog lead/leash in this context.

Because de agua here describes the type or contents of the bottle:

• una botella de agua = a bottle of water

This is the normal Spanish pattern:

• una taza de café = a cup of coffee
• una mesa de madera = a wooden table
• una botella de agua = a bottle of water

Using del agua would usually mean of the water, referring to some specific water already mentioned, which is not the idea here.

Llevar is a very useful verb that can mean:

• to carry
• to take
• sometimes to bring, depending on perspective
• also to wear, in other contexts

Here siempre llevamos la correa y una botella de agua means:

• we always take / carry the leash and a bottle of water

The basic idea is that you have those things with you as you go out.

So llevamos works very naturally here.

Yes, the order could be reversed.

This sentence starts with the cuando clause:

• Cuando salimos con el perro de mi vecina, siempre llevamos la correa y una botella de agua.

That is very natural. But you could also say:

• Siempre llevamos la correa y una botella de agua cuando salimos con el perro de mi vecina.

Both are correct. Starting with cuando puts the time situation first: Whenever we go out with the dog...

Also notice the comma after the initial cuando clause. In English and in Spanish, this is normal when the time clause comes first.

Both are possible.

• siempre llevamos
• llevamos siempre

But siempre llevamos is very common and sounds natural because siempre is placed before the verb to emphasize the habitual idea: we always take...

Spanish adverbs like siempre can often move around, but not every position sounds equally natural in every sentence. In this example, the given word order is very standard.

Yes, cuando can be followed by the subjunctive, but not in this sentence.

Here it refers to a habitual, repeated action, so Spanish uses the indicative:

• Cuando salimos con el perro..., siempre llevamos...

The subjunctive is used after cuando when talking about a future or not-yet-realized action:

• Cuando salgamos con el perro, llevaremos agua.
• When we go out with the dog, we’ll take water.

So:

• habitual / general → indicative
• future / pending → subjunctive

That is why salimos is correct here, not salgamos.

Yes, salir can mean to leave, to go out, or to head out, depending on context.

So cuando salimos con el perro de mi vecina could be understood as:

• when we go out with my neighbor’s dog
• when we head out with my neighbor’s dog

In this sentence, the context of taking the leash and a bottle of water strongly suggests going out for a walk, so go out is the most natural interpretation.