Unless you know people theres not a lot to do in Sao Paulo, but the night life is awesome if you're into that kind of thing. Girls are easy to talk to, at least if they speak English, and not all of them are after you just for your money, especially in Sao Paulo. Rio can be another story depending on where you go, but I've met plenty of nice girls there too. As for it being dangerous, its not as safe as most American cities, but its not really that bad as long as you don't venture into the really bad parts of town, and even then you'll be ok going most places during the day. Just be smart and stay aware of your surroundings and you'll be fine. Mr Spooners advice is good, although a bit over cautious if you ask me. There are lots of places in Sao Paulo where I wouldn't have a problem walking after dark, but like I said, stay aware of your surroundings. I could tell you all kinds of things about Brazil, especially Sao Paulo (I lived there for most of last year), but I'd be writing for days and I don't have time now. Lemme know if you want to know more.