You should be safe if you stay in the downtown tourist area which includes La Zona Norte, the red-light district. It is also called La Zona de tolerancia. Mostly it is just referred to as La Zona by us mongers. Usually, if you just use the term La Zona and you are a gringo, the locals, especially the taxi drivers will know exactly what you are referring to. Do some snooping about here and you will quickly learn how to get to where the action is.