Most flights arrive in Dublin airport and from Dublin city centre (and the airport) there is a Bus Eireann service to Ballyshannon here and then you can get a taxi or local bus to Bundoran here. From Galway there is a Bus Eireann service to Bundoran here. There is a bus from Belfast but you need to change in Enniskillen. To access the surf you can walk to Tullan and the peak but you probably need to rent a car for most other spots. In summer this is fine as Tullan is the main spot, but in the other seasons a car is recomended.