Learn Hardcore Portuguese (Portugal): Ela prefere estacionar no piso de cima, porque a saída é mais rápida. - She prefers to park on the upper floor, because the exit is faster.

Yes. European Portuguese is pro‑drop, so you can say Prefere estacionar no piso de cima... if the subject is clear from context. Without context, prefere is ambiguous (it could be he/she/you-formal), so keeping Ela avoids confusion.

Why use prefere and not gosta de?

Preferir expresses a choice between options (she prefers X over Y).
Gostar de means “to like.” Both are grammatical, but the nuance changes:
Ela prefere estacionar no piso de cima... = She consciously chooses that option.
Ela gosta de estacionar no piso de cima... = She likes doing that (not necessarily a comparison).

Do I need to specify the car after estacionar (e.g., o carro)?

No. Estacionar can be intransitive (just “to park”) or transitive (“to park the car”):

Intransitive (common in speech): Ela prefere estacionar no piso de cima.
Transitive (explicit): Ela prefere estacionar o carro no piso de cima.

What does no mean here?

No = em + o (“in/on + the”). Other contractions:

na = em + a
nos = em + os
nas = em + as

What exactly does piso de cima mean? Could I say andar de cima or piso superior?

piso de cima = the upper/above floor (natural in parking contexts).
andar de cima = “the upstairs floor” (very common for buildings in general).
piso superior = “upper level” (more formal/signage style). In Portugal, andar is very common for “floor,” but car parks often use piso on signs.

Why de cima and not em cima?

de cima = “of above/upstairs,” used to modify a noun: o piso de cima, o vizinho de cima.
em cima = “on top (of),” literal location: O livro está em cima da mesa. So you want piso de cima, not piso em cima.

Is the comma before porque required?

Not required. With or without comma are both possible, with a slight nuance:

No comma (common): Ela prefere... porque a saída é mais rápida. (gives the essential cause)
With comma: Ela prefere..., porque a saída é mais rápida. (more explanatory/afterthought feel) Your sentence is fine either way.

How do I choose between porque, porquê, por que, por quê in Portugal?

porque = “because” (conjunction): Ficou em casa porque chovia.
por que = “why” in direct/indirect questions: Por que chegaste tarde? / Não sei por que faltou.
porquê = noun “reason,” usually with an article: Não entendo o porquê.
por quê (with accent) is not standard in EP except as the noun porquê; the word-final accented “por quê” form is Brazilian usage.

Why a saída and not à saída?

a saída = “the exit” (definite article + noun).
à saída = contraction of a + a (“at the time of leaving/at the exit”): À saída do parque, vira à direita. Your sentence states a property of the exit itself, so a saída is correct.

Why does rápida end in -a?

Adjectives agree in gender and number with the noun. Saída is feminine singular, so:

Feminine singular: rápida
Masculine singular: rápido
Feminine plural: rápidas
Masculine plural: rápidos

Could I say A saída é mais rápido?

No. Saída is feminine, so the adjective must be feminine: A saída é mais rápida. But if you use a clause or verb where “fast” is an adverbial idea, you’d use:

É mais rápido sair do piso de cima. (neuter/masculine by default with the infinitive idea)
Sai‑se mais depressa do piso de cima.

Is mais depressa more natural than mais rapidamente?

In everyday European Portuguese, depressa is the go‑to adverb for “fast”:

Very idiomatic: Sai‑se mais depressa.
Rapidamente is correct but sounds more formal or careful.
Use the adjective with nouns: A saída é mais rápida.

Why é and not está in a saída é mais rápida?

Ser expresses inherent or generally valid characteristics; estar is temporary. The idea here is a general fact about that exit, so é is appropriate. Está mais rápida would imply a temporary, unusual situation.

Can I start a sentence with Porque in Portuguese?

Yes, you can: Porque a saída é mais rápida, ela prefere estacionar no piso de cima. It’s fine in both speech and writing (though very formal writing may prefer other connectors like Como at the start).

Any pronunciation tips (European Portuguese)?

Approximate EP pronunciations and stress:

Ela [ˈɛ.lɐ]
prefere [pɾɨˈfɛ.ɾɨ] (stress on FE)
estacionar [ɨʃ.tɐ.sjuˈnaɾ] (final -r is soft)
piso [ˈpi.zu] (final -o sounds like “oo”)
de cima [dɨ ˈsi.mɐ]
porque [puɾˈkɨ]
a saída [ɐ sɐˈi.ðɐ] (the í is stressed; the intervocalic d is a light [ð] for many speakers)
rápida [ˈʁa.pi.ðɐ]

Is piso the only word for “floor” in Portugal?

No. Both are common:

andar = floor/storey in buildings generally: moro no 3.º andar.
piso = also “floor/level,” especially in car parks and signage: Piso -2, Piso 0, Piso 1. For your sentence in a parking context, piso de cima sounds very natural in Portugal.