Possible things to do by day:
- Kilmainham Gaol has been said. Guinness storehouse, Trinity college, Newgrange, all on the east coast. Temple Bar is a shocking rip-off but if you want an atmospheric place to drink and do drugs then...

- Phoenix Park; you can rent out a bike for the day for around €7 and cycle Europe's largest inner-city park. Good place for a picnic. Wildlife, the President's house and the zoo all together.
- Croke Park; not just a venue for U2 (or Westlife...) concerts. The GAA is in full swing around that time of year so recommend going for a match if you can. Tickets are pretty cheap too. Bring nose plugs because its well known that people from the Irish countryside smell.
- Best chance of seeing a U2 band member may well be Bono who lives in Killiney. Goes to Finnegans pub down in Dalkey Village a fair bit. Seen his daughter Eve in the other pub (Queens) a couple of times. Nice area, probably worth a visit even if you don't get to see them.
Have heard that Bono & Edge usually go for dinner in the main village once a week, sometimes with someone like Neil Jordan, though have never seen them on my nights out. Larry lives up in the other end of the city (Howth) as far away from Bono as you can get and haven't a clue about Adam.
Pretty sure you can leave a sign on Bono's front gate.
Dunno, anyway you looking forward to it?