You have to be careful in São Paulo, no doubt about it. I don't live there, but I've been spending the last couple of months in Brazil and mainly in São Paulo. Walking the streets with an M9 there can be quite nerve wrecking at times, but there are many areas that are more than safe enough, at least at daytime. It is however a good idea to do some research on the different areas before waving your camera in public. I was taking pictures in what appeared to be a safe area just by Avenida Paulista and was about to walk down a very interesting and photogenic street, when I was stopped by a guy who said "do NOT go down this street with a camera!!". Turned out that was a very bad street, and quite impossible to tell without knowing.
If you're gonna move there, I'm sure you'll find a way to roam the streets there. It's a huge and very cool city. I'll be following this thread to see if there is any more good advice showing up.
Cheers
Arnulf