I just came back from my short weekend trip to Dublin and of course I visited some U2-sights. First of all I saw the Bonavox Hearing Aid store, where Bono got his name from. It's just off O'Connell Street (Earl Street North, to be exact), very easy to find. If you walk along the Liffey, you'll find the Clarence on the south side, a bit after the Ha'penny Bridge. I also made a walk to see Windmill Lane Studios, but the area isn't very nice. Because the weather was fantastic, we decided to take the DART and headed for Killiney, where Bono lives. After a foto of the famous gates, we walked the way to the next town, Dalkey. It's a very scenic stroll along the coast, very beautiful.
Dublin is a fantastic city! Enjoy your stay and I wish you a nice time there!