I'm here in Sao Paulo, Brazil for work and just wanted to share with you my experiences eating in Sao Paulo, Brazil. All the recs below were suggested by my local coworkers. I told them that I wanted to eat and experience food like a local.
Italian: Famiglia Mancini. It's like Buca Di Beppo in the States but sooOOOOooo much better. Portions are large (feeds 2 and ~ 45 reals per portion) and the quality is quite high. 90%+ local folks having food times and food. Very lively crowd. English menu is horrible. Just point at pictures and eat.
Pizza: Margherita Pizzeria. They said Brazilian Pizza is some of the best in the world and that 2 million pizzas are sold to Paulistanos (people who hail from Sao Paulo) each weekend. Ranking against my favs -- Lou Manetti's pizza in Chicago, First Class Pizza in SoCal and Village Bakery in Davis, CA -- I have to say you have to try it. It's more cali-style pizza with really fresh, hearty toppings. 80%+ local people. Great place for large groups of people. ~45 reals per pie.
BBQ: Jardineira Grill. If you gotta eat churrascaria, my local friends say you go here. They had something like 10+ cuts of beef, lamb, pork, etc etc and seafood and dessert. All top notch. I heard it's the place where people take foreign execs out (and it shows, very international set of customers). ~120 reals for all you can eat.