Their food isn't very different at all, although since I stayed in farmhouse b&bs, it was fresher than what I am used to. Black pudding, a breakfast food is...an aquired taste. Irish Stew is delicious but nothing exotic. The bacon that I had is more like ham. You will be very pleased with how friendly people are.

I am not much help with the rest of your question since it has been a while since I have been. I started out in Dublin and made my way around the ring of Kerry. I wasnt fortunate enough to make it north enough to see giants causeway. Off the top of my head, I remember I visited Wicklow, Cliffs of Moher (amazing), Killarney (really nice), Dingle, Kilkenny (a great medieval city if you have the time), and Doolin (it was filled with a midge (tiny fly) infestation of biblical proportions during my visit). I left Dublin immediately since I don't care for big cities. I have been to 30 countries and Ireland is the only one I plan to visit again. It is not that I dont like the other places. It is just that in general, I would like to see countries I havent seen yet.