I've never had a problem with the english accent at matches (only slagging from Harps)...
Personally,
Pats: I find their fans generally the soundest and McDowells is the best pub, and this season they're playing alright stuff.
Bohs. Most fans okay, if arrogant (see above), but they have a habit of internal bitch fights
Shels. Unless you're 16 wouldn't bother
UCD. Unless you're a rugger bugger trying to be hip by being uncool, I wouldn't bother
Rovers. Generally sound enough (despite what some would have you believe), and if you enjoy a siege mentality they are the ones for you.
Dublin City. Unless you're a loner, who likes franchise football don't bother.
Bray. They're South County Dublin as well, but why bother?