There are the super rich, the rich, the middle class, the poor and the very poor. Each of these classes have their own housing areas, way of living, way of shopping, way of entertaining themselves. Problems normally arise when you stray over these boundaries. As a foreigner there is no way that you can merge into the background, people know you are well off. Following these simple rules we managed to live in and enjoy Sao Paulo immensely with no problems for five years.
Brazil is a hot country, and it is safer to drive with windows shut.
If you are unfortunate enough to be stopped do not panic, do everything that is asked of you, give him everything that is asked for. This includes watches, wallet, wedding rings, ear rings, car keys etc. He will be more nervous than you so the key thing is to stop him panicking. The second thing that people think about is money. Money in Brazil has in the past been complicated by the unstable economy.