I find that if I'm singing something Irish, I can usually get away with doing it in straight English, though sometimes a little inflection creeps in--I also pick up accents unconsciously. (As a native of Illinois, I spent the summer with relatives in Kentucky, and upon returning to elementary school, I was put in speech therapy for a defective "R" sound, thanks to my aquired Kentucky accent!) I have found that Scottish songs are much more likely to depend on dialect for proper rhyme or rhythm. I try to do it with as little accent as I can get away with, sort of like someone who's lived in the States for years but still has just a trace of accent left--that way I don't feel like I sound too dorky.

I was shocked but pleased one night after singing an Irish song with just a little inflection when an actual Irishman came up to me and told me I had just transported him back to Belfast. So I guess it didn't sound too dumb.