My wife and I will be landing in Dublin in July, we plan to rent a car then stay in Belfast for two days then on to Newcastle to hike Slieve Donard. I heard its rough driving in the city of Belfast any advice on where to stay on the outskirts? We are mainly going to visit the peace walls and then the giants causeway. After Newcastle, we are heading south for a 5 day hike on the Kerry Way, then back to Dublin.
Make it easy on yourselves. Bus or train ( 2 hrs ) from Dublin to Belfast, see Belfast, then rent the car.
If memory serves there is an Enterprise agency near the M1 outside the city which would be ideal since you are heading to Newcastle.
We've stayed at Somerton House B&B, which is on the outskirts, in a residential area. It's about 5 minutes from Belfast Castle. Nice place, great breakfast, and the owner, Mannix, was very nice.
Keep in mind that there's a lot to see on the drive from Dublin to Belfast.....the Mourne Mountains, Silent Valley, Green Castle, Castle Roche (fantastic), Carlingford, etc.
Since you're into hiking, in addition to seeing the Giant's Causeway, make sure to visit Kinbane Castle....stunning location.