You know, I usually LOSE weight on vacations, and I never know how.
Try to keep a mental note for everything you eat. Make sure you try to stay low cal. Like, if you're getting ice cream, don't get the triple scoop, on a waffle cone; get the single scoop in a bowl...restaurant wise, try to stick with sandwhiches, (like the BLT is always good
You can sometimes ask for low-fat mayo too) soups, or salads. Fast food places, I know at mcdonalds, their mcchickens are yummy, and under 500 cals.
Really, your goal should be to MAINTAIN your weight
Don't plan on losing 10 pounds while you're there. If you maintain, You are good! If you gain one or two pounds, what the ****. It was a great vacatioN! For exercising, well, definitely don't TRY to excercise. Your body needs time to heal itself, and, well, your body is sure smart enough to not go into, "let's gain weight" mode.