omba_de wrote:If you'd travel to Austria, I could tell you where to get cheap data SIM cards. But Ireland... Sorry. No clue.
Go into any phone shop (there are four main carriers: O2, Vodafone, Meteor and Three, and they all have shops on main shopping streets in most towns and cities) and ask for a prepaid SIM (make sure to get the right size SIM for your phone). You'll pay maybe ten euro, but the SIM will have a few euro of credit pre-loaded on it.
For the record: the map in Ireland is very complete in and around Dublin. Most of the major cities are fairly OK, but the quality of the map in regional towns depends a lot on how good the satellite imagery is in the editor for those towns, because obviously it's hard to map towns without good satellite images. Motorways, major highways, and main roads are all fairly complete in most areas.
Enjoy your trip!