I've been to Sao Paulo dozens of times. I have many friends who lived there, walked around freely, and drove their own cars. There is no need for a driver or a guard unless you're a well-known public figure or drug dealer. It's not Tokyo, but it's no more dangerous for a tourist than New York.
That said, the best neighborhoods are Moema and Jardins, though Itaim Bibi is up-and-coming and has a lot of the most exciting restaurants. Ibirapuera Park is lovely as well; if you have time, it's worth a walk around.
