Bands who sell out shows from Ireland to Appalachia and headline SF's Hardly Strictly Bluegrass festival jam here on weeknights, taking breaks to clink pint glasses of Guinness at long union-hall tables. Mondays compensate for no live music with an all-day happy hour, plus free pool and blarney from regulars; expect modest cover charges ($6 to $14) for barnstorming weekend shows.