i figured i'd post a reply to this thread, even though the vegas trip has obviously come and gone - jus tin case any one else going to vegas soon happens to see the thread and check it out.
vegas is actually one of the easiest places to stick to the plan because they have SO much food there!!! Sushi is doable (fish, steamed white rice, salad no dressing) and is everywhere in vegas! There is a Whole Food Mkt in Henderson south of town so you can stock up on healthy stuff. Also, the Venetian has the Canyon Ranch Cafe - specializes in healthy food so they will prepare anything exactly the way you order it. it's a breakfast/lunch only place - they will make you an egg white omelet with fresh veggies, no oil or butter or salt.
The #1 way to stay OP in vegas is to wake up when you normally wake up and go to bed when you normally go to bed. Being awake until 4am means you're going to be hungry and tempted to cheat!
Also, i suggest a quick trip to nearby Red Rock Canyon or Mt Charleston - there are some incredible hiking trails out there so you can get some exercise. Otherwise, almost any casino/hotel in vegas has a fitness center.
If you find yourself stressed over whether or not you can stick to the Plan, go for a nice massage at one of the spas on the strip and just relax and think about being good to yourself!