Is the Westin the one by South Coast Plaza near the South Coast Repertory? If it is you could probably just park at the South Coast Plaza parking lot. We always park there and walk across the street to catch a show. When we leave after 11pm there are still a ton of cars in the giant parking lot near Bloomingdale's. I am sure there are employees working over night to restock items or people came to the bars/restaurants and met someone and left one car there overnight.