In São Paulo and another big cities you can find many vegetarian restaurants.

There are good vegetarian, and even vegan, restaurants to be found all over Brazil. In March, I was in Porto Alegre for two weeks. We tried a different veg restaurant every day, and still I think we missed a few. Then we spent two weeks in tiny Itacare, Bahia, which has a middle-eastern veg restaurant. You'll find the best choices in Rio and Sao Paulo, of course, but also in many smaller cities, such as Iguacu or Parati. Pick up a copy of the glossy magazine Revista dos Vegetarianos for pretty complete listings in the back. The biggest problem is that, by some bizarre convention, many veg restaurants in Brazil are not open evenings.