I was in Barcelona last January. I found the Ramblas to be fine to walk down during the day. At night though, I have to admit I sometimes felt a little uncomfortable because of the prostitutes. I had no problem with them being there but I did not like being followed by them. Some of them even tried to grab my arm and got in my face a bit, which I frankly found intrusive and agressive. It's shame because I think it is a lovely walk but it is a top tourist zone and those areas attract all kinds of people.