I was last there in 2008/2009 and the euro was killing the US dollar so that changed things but the exchange rate seems to be better now. Pints are 2-4 Euros, the further you get out of the city the cheaper. I was with my brothers and we basically lived on Guinness, Paddy Irish whiskey and kebab on our last trip. Our money was spent on hotels, train and bus tickets.
I'd say don't get stuck spending too much time in Dublin, I think you can do most of the touristy stuff in Dublin in two days. Definitely head to Galway, Lahinch is close to the Cliffs of Moher that was cool to see. It's beautiful up north in County Donegal and I've heard Belfast is safe these days, I'd go there.
The water will be freezing all year long but they have a surf shop in Lahinch that probably rents wetsuits.