Dublin, Ireland could be fairly cheap, with exception to food. Food could get pretty pricey there. You need to be savvy when it comes to that. But, do you mind staying in a hostel? 'Cuz I bet it wouldn't cost you any more than a trip to California. And, I've gone there on my own. Why would you need to depend on friends going with you on a trip to Ireland?
Actually I'll clarify... Dublin is pretty pricey with all the financial stuff that goes on in that city, I reckon... but flight and hostel part of travel expenses won't add up to all that much. Watch your wallet with other expenses or yes, you could blow through your money really quick there.