12/24/2010 AT 03:00 PM EST
, dining with a female friend and an elderly couple at the Bazaar at the SLS Hotel
in L.A. The group arrived (and left) in her SUV, and Cyrus was having a "blast and cracking jokes at the valet stand after her lengthy dinner," an onlooker says. The teen star was also "very friendly" and "interactive" with staff and restaurant guests.