Make sure you watch your personal belongings as pick pockets and purse snatching are a huge industry there.
But - it was one of the better places I have been. Architecture is amazing as well as all of the food. They have the most amazing coffee and I miss it to this day. I agree w/ the plan on staying out late cause they do stay out late and eat late. You can rent bike (at least you could about 5 years ago) and take a bike tour. That was really great. On a nice day being able to tour around on a bike. IMHO, skip Olympic village, it was not anything overly interesting. However, there are some nice restaurants around there.
If you know spanish (like in my case, the mexican kind) and you attempt to speak to them, they 1) find it hysterical and 2) seem to really want to go out of their way to help you. We got some of our best suggestions from just talking to people who were sitting around having coffee in a cafe w/ us.
And as for the prior poster that said
Paris walks all over Barca
I don't think so!!!! Paris is second rate to Barcelona!