Many senior and middle ranking Brazilian business executives speak excellent English and in fact many of them may have studied abroad in the USA or Europe.
However, English is by no means universally spoken and when dealing with people outside the major commercial centres, an ability to speak Brazilian Portuguese is extremely useful. (Try to avoid using Spanish as this can be seen as culturally insensitive. Brazilians are proud of their uniqueness in South America as non-Spanish speakers.) If doing business in Brazil for the first time, check out whether you will need a translator or not.
As with many Latin countries, communication tends to be predominantly oral rather than through the written word. Brazilians tend to put the spoken before the written word. When sending something in a written format it is usually a good idea to follow it up with a phone call or a visit.
Verbal communication in Brazil can often be viewed as being theatrical and over-emotional by those cultures which place a great significance on the maintenance of professional reserve in all situations. In a country like Brazil, if you feel something strongly, you show it. Overt signs of emotion definitely do not imply lack of conviction and should be taken as the deeply felt belief of the speaker.
The use of significant amounts of exaggerated body language (by the standards of less tactile cultures) plays a significant role in normal communication. Brazilians are very tactile — even across the sexes — and work at very close proximity. They also exhibit strong levels of eye contact when speaking to people. This combination of tactility, proximity and a steady gaze can be intimidating for some (many Asian cultures for example), but it is important that you adapt to these issues as quickly as possible otherwise your own reserve could be misinterpreted as unfriendliness.
Be careful when using humour in very serious situations as it can be viewed as lacking in gravitas. However, in everyday situations it is important to be seen as good company and entertaining. Life is to be lived and enjoyed.