WEEKEND PLANNER: Jason Bracelin puts up a defense of Keith Urban (Saturday at Mandalay Bay). Il Divo pitches for the Josh Groban set (Friday at Mandalay). Demi Lovato and David Archuleta (Saturday at the Orleans). Tears for Fears (Saturday at Green Valley). The Fray (Friday at Palms). Clutch (Sunday at House of Blues). Rick Thomas brings tigers back to the Sahara. And Heidi Knapp Rinella reminds the world of the Vegas staple, Luv-It frozen custard.