Your 12 hour layover is long enough for you to travel pretty much anywhere in LA for a session. For a great incall GFE session, I highly suggest you consider Platinum Connections (recently merged with Enjolie Dating Service) http://platinumconnections.com , especially Brooke, Megan or Victoria (check their reviews on TER). Platinum has incall locations in West Los Angeles and Santa Monica. A little on the high side price-wise but worth it for young hardbody GFEs.