Antes de salir, reviso si llevo el abono en la cartera.

Because antes is followed by de before an infinitive.

• antes de + infinitive = before doing something
• So antes de salir means before leaving / before going out

This is a very common pattern in Spanish:

• antes de comer = before eating
• antes de dormir = before sleeping

If you use a full conjugated clause instead, you normally use antes de que:

• Antes de que salga, reviso... = Before I leave, I check...

Because after antes de, Spanish normally uses the infinitive when the subject is the same as in the main clause or when the subject is general/understood.

Here, reviso and salir both refer to I:

• Antes de salir, reviso... = Before leaving, I check...

Spanish prefers the infinitive in this kind of structure, where English often uses before leaving.

Spanish often leaves out subject pronouns because the verb ending already tells you who the subject is.

• reviso = I check / I go over
• The -o ending clearly shows it is yo

So yo reviso is possible, but usually unnecessary unless you want emphasis or contrast:

• Yo reviso, pero él no. = I check, but he doesn’t.

The present tense here expresses a habitual or routine action.

• Antes de salir, reviso... = Before leaving, I check...

It means this is something the speaker normally does, not necessarily only one specific time. Spanish uses the present for habits just like English does:

• Cada mañana, tomo café. = Every morning, I drink coffee.
• Antes de salir, reviso... = Before leaving, I check...

Here si means whether, not a conditional if in the usual sense.

• reviso si llevo el abono = I check whether I have my pass on me

This is a very common use of si after verbs like:

• ver = to see
• preguntar = to ask
• comprobar = to check
• revisar = to check/review

Examples:

• No sé si viene. = I don’t know whether he’s coming.
• Mira si está abierto. = Check whether it’s open.

So in this sentence, si introduces an indirect yes/no question.

Because llevar often means to have something on you / to be carrying something, not just to carry in a physical, active sense.

So:

• llevo el abono en la cartera = I have the pass in my wallet / I’m carrying the pass in my wallet

This is very natural Spanish. Compare:

• ¿Llevas dinero? = Do you have money on you?
• No llevo el móvil. = I don’t have my phone with me.

Using tener would change the nuance. Tener means possession in general, while llevar suggests you have it with you.

In Spain, abono often means a travel pass, especially a season pass or monthly pass for public transport.

On its own, abono can have different meanings in Spanish depending on context, such as:

• subscription
• pass
• payment/installment
• even fertilizer in other contexts

But in this sentence, especially with en la cartera, it most naturally means a transport pass or similar pass/card that you keep in your wallet.

In Spain, you will often hear:

• abono transporte = transport pass
• el abono = the pass, when the context is clear

In Spain, cartera often means wallet, especially in a sentence like this.

However, cartera can also mean other things depending on region and context, such as:

• wallet
• purse
• briefcase
• school satchel

Here, because the sentence mentions el abono being inside it, wallet is the most natural interpretation.

This is a good example of how Spanish words can be broader than a single English translation.

Spanish uses definite articles much more often than English does.

So where English might say:

• my pass
• my wallet

Spanish may naturally say:

• el abono
• la cartera

especially when it is obvious whose items they are from the context.

The sentence already implies I am the person checking, so Spanish does not need to repeat possession as often as English does.

You could say mi abono or mi cartera, but it is often less natural unless you want to stress ownership.

Spanish often puts the time expression first to set the scene:

• Antes de salir, ... = Before leaving, ...

This is very natural and matches English quite well. You could also change the order:

• Reviso si llevo el abono en la cartera antes de salir.

That is grammatically correct too. The original version sounds slightly more natural if you want to emphasize the routine that happens before going out.

Because Antes de salir is an introductory phrase at the beginning of the sentence.

In Spanish, a comma is commonly used after this kind of opening phrase, especially when it is a clear setup for the main clause:

• Antes de salir, reviso...
• Por la mañana, estudio.
• Después de comer, salimos.

You may sometimes see short introductory phrases without a comma, but here the comma is standard and helpful.

Yes, you could, although the nuance changes slightly.

• revisar = to check, go over, inspect
• comprobar = to verify, check, make sure

So:

• Reviso si llevo el abono... sounds like I check/look to see whether I have the pass
• Compruebo si llevo el abono... sounds a bit more like I make sure / verify whether I have the pass

Both are possible. Reviso sounds very natural for a routine pre-leaving check.

Not with the same meaning.

• antes de salir = before leaving
• para salir = in order to leave / for going out

So antes de salir expresses time, while para salir usually expresses purpose.

Examples:

• Antes de salir, reviso todo. = Before leaving, I check everything.
• Me preparo para salir. = I get ready to go out.

So para salir would not work as a direct replacement here.