Sao Paulo has some amazing street art. You can see bits and pieces all over the city but by far the biggest concentration is in the Vila Madalena area.
Take the metro to either Fradique Coutinho or Faria Lima (both on the yellow line) and walk around from there.
The first place to head is Batman Alley, where there is a ‘legal’ street art area. It was a bit crowded when I went (on a Sunday afternoon) but still an amazing place to see.
From there you can walk around the neighbourhood and you will see murals and all kinds of art projects (the area also contains a lot of galleries, but they were closed when I went there on a Sunday)
Early Sao Paulo graffiti was largely political slogans; it emerged out of living under a dictatorship and the people needing to express themselves.
*If you’re in the mood for more free art, the MASP on Avenida Paulista offers free entry on Tuesdays, and Pinacoteca do Estado, close to Luz station, does free entry on Saturdays.