Hi I will be in Dublin on the 30 of April this upcoming year and am then planning to make my way to Portrush in order to see The Giant's Cuaseway. I was wondering what form of transportaion would be the best other then driving a rental car. Are there any buses or train services that could do the trick?
Welcome to my forum. Please go to my Transport page for links to public transportation in Ireland. With them you can input your data and get the exact info you need. You can certainly take a bus or train to Belfast and a tour to the Giant's Causeway from there on your own.
There are a couple of tours that depart from Dublin:
You can certainly get to Portrush by train and Bus but as Michele has said you can get tours from Belfast or Dublin(long day these). This link might also help.