Instead of Chinatown, in Sao Paulo there is "Japantown."  In this neighborhood, you get a really interesting perspective of what happens when Japan and Brazil come together.  On Sunday there's a fun market with all kinds of items and foods.  You can find excellent sushi, but make sure to ask for recommendations before you go.  Try the ice-cream/popsicle "Melona," which you can find at almost any market - delicious and refreshing.  The best way to get here is by taking the subway, as it is very difficult to find parking.