Monday nights are the Contemporary Jazz Orchestra Big Band nights at North Beach mainstay Jazz at Pearl's. They play the classic jazz orchestra works (Ellington, Mingus) and also some hard bop. Two shows (one at 8, one at 10), $15 + 2-drink minimum, 256 Columbus (x Pacific). Other events: --Salsa and swing dance lessons at Julie's Supper Club, with burlesque performers on the hour. 8-11 p.m., $6 after 8 p.m. (half hour lesson), $10 by......