It's safe considering It's a not so small city. Don't go out at night except bairro alto etc..of course. Ladies cross your bag over you (don't know how to say it in english..) and everyone don't flash your stuff, even If you're flashing on a secure area you can be followed. I'm from lisbon, born and live there and I do that so If you're turíst the more reason you should do that, I think :) and about drug dealers don't be baby about it, they try to sell you, so what? you smile and say you no and they'll move to the next person. It's not like they're big dealers they just sell to kids in bairro alto and such because they know kids smoke drugs, they don't sell cocaine or anything like that.