See the ABOUT SPAIN forum for some specifics. In general it is VERY safe to travel around alone. Just be prepared for MEN to talk to you, if you are in a cafe/bar, waiting at the train station, etc. Usually it is either at a distance-- a piropo, like guapa -- or just friendly chat that you can continue or just not engage in. The main precautions for women are the same for tourists: watch for the pickpockets, keep your belongings locked up, stay out of questionable areas if you don't know where you are going, don't walk around drunk (seriously. ALL the problems my women students have had occur when they have been drinking, and then meet up with untrustworthy sorts). In hostels, make sure your room locks securely. That's about it! Have fun!