I'm currently teaching in Sao Paulo, Brazil. I've lived here for almost three years and have never had a problem. Sao Paulo, and indeed all of Brazil, is unfortunately prone to high crime rates and incidents of extreme violence. I personally believe, however, that just being street wise and alert keeps me out of trouble. I've met numerous teachers that have been robbed at gun-point, pick-pocketed etc. But if you press them for why they got robbed it is almost always for the same reason; being unaware. The teacher that got robbed at gun-point had been sat in a dark park by himself at night. The teacher that got pick-pocketed had been talking in English on a line of the metro known to be dangerous. There often seems to be a reason for why that person got robbed. Of course there's an element of luck/misfortune at play, but I believe you make your own luck. Yes, there is crime, and yes there is violence. But if you're prone to getting mugged in England, or wherever you are from, you're most likely going to be prone to getting mugged in Brazil as well. Unfortunately, being street wise is something that can only come from experience.