The official language of Brazil is Portuguese, spoken by the entire population (except a few very remotely located Indian tribes, and some recent immigrants). Brazilian Portuguese has a number of pronunciation differences with the language spoken in Portugal, but speakers of either can understand each other. However, European Portuguese (Luso) is more difficult for Brazilians to understand than the reverse, as many Brazilian television programs are shown in Portugal.

Note that a few words can have a totally different meaning in Brazil and Portugal. An example of this is "Rapariga" which in Portugal means young girl, and in Brazil mean prostitute.

"Legal" (leh GAL) is slang meaning that something is "great" or "cool" -- not that it's lawful to do. It could be very illegal! Also, "no" doesn't mean "no" as in English and Spanish, but rather "in the" as a contraction of em + o (en el in Spanish). Não falo Inglês no Brasil. I don't speak English in Brazil.

English is not widely spoken except in some tourist areas. One can always find a way to get around, especially among students and in financial zones. Don't expect bus or taxi drivers to understand English, though. In most big and luxurious hotels, it is very likely that the taxi fleet will speak some English.

Spanish speakers are usually able to get by in Brazil, especially towards the south. Whereas the written language is quite similar to Spanish.

Body language

Brazilians use a lot of body gestures in informal communication, and the meaning of certain words or expressions may be influenced by them.

The thumbs up gesture is used everywhere and all the time in Brazil.
The OK gesture (thumb and finger in a circle), on the other hand, may have obscene connotations in Brazil. Avoid it if you can, people may laugh at you, or be offended (usually if they are drunk). Use thumbs up instead.
A circular movement of the forefinger about the ear (a gesture that Germans use to indicate telephone for you) means you are crazy!, the same as in English.
Stroking your two biggest fingers with your thumb (as the French do to say something is expensive) usually expresses a very long time.
Touching the palm with the thumb and making a circular movement with the hand means I am being robbed! (sometimes meaning that some price is too high).
The Hush gesture is considered extremely unpolite, just about the same as shouting "shut up!" to someone.
An informal way to get someone's attention (similar to a whistle in other cultures) is a hissing sound: "pssiu!" It is not perceived as unpolite, but gets really, really, REALLY annoying if repeated too often. They also call cats this way, rather than the kiss noise others (the French again) produce.