We are planning about 2 weeks in Europe and are planning to get the 21 day global pass, which includes Ireland. We were really hoping to avoid renting cars, is it possible to see Dingle and Dublin using just the railpass?
Don't know anything about global pass but you can't get to Dingle by train. You might be able to get to a city or town nearby using train and then take bus but not sure.
You can get to Tralee by train, I believe, then you'll have to take the bus the rest of the way to Dingle. You can see the town, but you really need a car to do the loop drive (or take a tour). I'm curious, though - why are you buying a three-week pass for a two-week trip?
Ireland via rail and bus is very limiting. Yes, you can combine them and get most anywhere but you'll be spending a lot of time on them that could be avoided with a car. Ireland is best done by car and trying to do it any other way limits your traveling ability more than anywhere else in Europe. Before you waste two weeks of a 21 day global pass, carefully research your itinerary. Make sure it works efficiently and gets you where you're going within reasonable times. With Dublin you don't need the railpass. The airport is there and "all" trains originate in Dublin. Most of the rail lines I'm familiar with will go in and out of Dublin. You will frequently, if not always, find that going from A to B in different regions of Ireland involves a change of trains in Ireland. This is very time consuming. Have I been negative enough? Some will disagree but my basic statement remains that you need to carefully plan your entire route. Ireland isn't England, France, Italy or Germany when it comes to rail transport.