I have been 4 times and love to eat and do eat whatever I want, but try to stay away from fried foods, and drink lots of water while we're there. The walking definintely helps, and on all 4 trips, I've had minimal weight gain, 1-2 pounds, but my main piece of advice is to enjoy yourself, but immediately upon return from vacation, get right back on program. The one time I didn't do that, the following week, I gained 6 pounds, so it does catch up with you.
The other thing that helped me is not having unhealthy snacks available in the hotel room. Late night snacking is one of my downfalls, and if it's not available, I can't eat it.
Have fun, and use common sense, and you will be fine.