A cross dresser would get on fine in the George or Panti bar, or indeed most gay bars in Dublin. You'll find almost no one will bat an eyelid at a CDer or do anything to make them feel uncomfortable, and you'll fit right in.
There are also groups out there that help if your nervous about heading out for the first time.
I've met many's a CDer out having a few drinks and meeting people, and it's mostly been a positive experience all round.
I will also add, don't be put off by people asking questions (if anyone does). They're probably not trying to be 'nosy' it's just you're dealing with a community that has drag queens, cross-dressers and, transgender people, all of whom have different preferences for things like how they wish to be identified.
Rather then accidentally cause offence, someone might ask you a bit about yourself in order to find out how you wish to be addressed for example. I find it's just a courtesy to ask and be respectful rather then be arrogant and guess.