my 18th...

I'd agree with the point that a lot of people making regarding the train fare effectively being the difference between the price of drinks in Dublin or Galway (your only real options assuming you're just coming for the weekend as Cork is a good five hours from Dublin on public transport).

If you're looking to just go out, get drunk and have a wild party, stay in Dublin and go to Temple Bar. You'll find loads of other English people there on stag and hen parties and it can be good craic if that's what you're into.

If you'd prefer to get an idea of what a more typical good night out in Ireland is, head to Galway, it genuinely is the party city of Ireland (just don't tell the stag and hen parties, we don't want them). There's a decent range of nightclubs and about a hundred pubs in the city centre. I'd avoid one thing Pighead suggested though, while Salthill used to be the place to party, the nightclub scene out there pretty much fell apart around three or four years ago so you'd be best to stay in town.

If you're into your rawk, head to Sally Longs (wear black), if you prefer R&B/Pop, head to the Living Room, the Cellar or the Kings Head. Most of the Clubs are similar enough but Cuba's your best bet if you prefer rock/indie and whatever you do, avoid Boo Radleys.