As Jim Carroll suggests, in Miltown itself, Friel's is the best starting point for music. Singers tend to congregate in Marrinan's - also in the town itslf - best time is late afternoon as it gets packed and downright unpleasant later, IMHO. You'll soon get to know the options. How long will you be in the area? If you're not familiar with Irish music, taking one of the two general introductory courses (on the instrumental and singing traditions respectively) may be worth considering.