I went for Labor Day week and went through exactly what you are contimplating right now...and I'm going back for New Years...
I planned on hitting the gym in my hotel 3x for the week I was there, brought Grow! bars, Grow! powder, and HOT-ROX. I figured I would do as good as I possibly can.
Well that went right out the window. I ate about 5 Grow! bars on my flight and that was about it. Never went to the gym, never ate good, didn't sleep (10hours total in 7 days) and drank like a fish and partied my ass off!
Now this was my first time there, pretty much my first vacation ever so I took advantage of it. I needed the break.
So for you, it depends on a lot of things. If this is your first time like me, trust me, you will forget all about everything while your there...maybe take some HOT-ROX to help ease the fat gain while you are there but just go and have fun. Hit the gym hard when you get back.
If you vacation a lot, go to vegas a lot, then do the best that you can. Try sticking to your diet whenever possible, but honestly I just don't see that happening.
What you can do which was talked about before going on vacation is to OVERTRAIN the week before so the break will do you good with all the food and carbs you will be consuming. Take that week to rest your muscles, take HOT-ROX and the most important thing of all is HAVE FUN!!!
When you get back, get back to your normal routine and you'll be just fine. If you are not in a competition, then don't sweat it. One week won't kill you as long as it doesn't snowball when you get back home.
Good luck and have a blast!!! I can't wait! 36 more days and I'll be there!!!