Try the Rosetta Stone Irish course. I did Irish at Gael Linn in Dubiln when I was living there, but found I just wasn't cut out for the "political indoctrination" BS that seems to accompany the teaching of Irish-- I was there to learn the language, not to be persuaded to vote Sinn Fein. Once you have a basic grasp of the language (and Rosetta Stone is excellent for that) you should be good to order a pint when next you're in Ireland. Although a word of warning: Most bar staff these days aren't from Ireland, so if ordering a pint it would be as good to know Lithuanian as Irish!