All I'd say is be very wary when in the main touristy bits like Las Ramblas in the evening. If a pack of girls approaches you being all nice and friendly they're actually pick-pocketing you. Was out there a few months back and one of the guys had his iPhone 5s and bracelet removed the first night after being a little the worse for wear.
It's a really nice city though and obviously not the only place such crime happens, I was just shocked how prevalent and blatant it was.
On the flip side, if you want you balls felt for free, empty your pockets in you hotel room, and go a wandering down las ramblas!
btw being serious, I don't know much about barca or place names I've been to, only been a few times, but generally avoid las ramblas, bloody irritating and expensive.