People don´t understand you on the streets? Talk to the youngs: it´s not rare to find an English-speaking one.
Portuguese is known as a very difficult language to speak and understand. But in a major city like São Paulo it is very easy to find English-speaking people in places of a reasonable level, like restaurants, bars and even stores.
If you are on the street and need information, forget about asking for taxi-drivers or passers-by. You would better talking to young people, which are very likely to speak good English. If that does not work, try some Spanish; this language is very similar to Portuguese and almost everyone will be able to understand you.
