Cuba is in general a very safe place, where you can walk around any time without having to worry much. Even so, as a very important tip, please be very careful when you're in Cuba with your money and belongings. Try to check first with the hostal or friends the money change or the things you want to do, but if you can't, try to always have the price of things set before accepting the service or product, and make sure to check and count your cuban money when you change, and in general be very careful if you're traveling alone and low budget and you're not getting much support.