I have to say, after visiting Barcelona, it is the BEST city in Spain. I think Madridman should consider a Barca.com instead (just a joke Madridi)
But anyways, like any big cities, keep any eye on your pocket.
But Barcelona for me was like San Diego. (if you've ever been there)
Many people speak english, the harbour is beautiful, there is some cool nightlife, and people are up early in the morning jogging or going to work on their scooters. It's very much like Southern California; minus the scooters.
Las Ramblas is cool and CHEAP (from dollar standards)
However, the better music scene seems to be down the road (about 3hours)in Valencia. If you're into modern music, Valencia was the only place that really rocked in THEIR OWN STYLE. But I, as an American, felt most connected to the Catalans.(I know the Spaniards out there that are reading this are vomiting)Buuuuuut, I guess the best thing I like about Barcelona is that they really balance "Spanish" life and "American Business" life incredibly. You can eat both American AND Spanish fast food. (in Valencia too) Enjoy your stay and if you say this to everybody you will be their best friend: VISCA BARCA!!!!!!!!