SF borrows shamelessly from global cultures. This Saturday starting at 1:30 at the Northstar Cafe in North Beach you can join in with other ambling, dancing marchers following the North Beach Brass Band around Washington Square for a raucous Line Dance celebrating Mardi Gras. Get your free beads and head out, ending up at Tupelo on Grant Avenue where the conviviality continues with beer and free jambalaya and red beans and rice until the early evening.