Most bars in Barcelona are located close to each other, in an area often called "Gayxample". It is close to metro Universitat. You find here most bars, some saunas and clubs. There are not so many restaurants in this part of town.
Barcelona gay nightlife starts very late. This also includes the bars. Tourists usually go out a bit earlier and can be found in Punto BCN. The spanish guys don't show up before midnight or later.