Mick, have a look at the EasyJet and Ryannair sites. If you can find a cheapish deal to London, you might find an onward flight to Dublin or Belfast for 50 dollars or less. Then again, without knocking Portaferry at all, when you're coming so far it might be better to wait for something in a more spectacular location, or latched on to the side of some existing festival - Fiddlers' Green at Rostrevor, maybe? And a slightly more clement time of year might make sense, though that's obviously relative in Ireland.

I'm glad Fib's gone into all that detail about road directions, by the way. I was overlooking that people who don't know the roads are going to find it amazingly easy to get lost.