Do the best you can with what each situation hands you. If you go have pizza, there probably is a salad on the menu as well--so start with a salad--and eat less pizza. Wherever you go to eat, there are bound to be "best choices" on the menu, and veggie dishes. If at a steak restaurant, have it, and a baked potato with a little something on it, and a side of veg--or skip the potato altogether. As to the drinking, perhaps have 1 of something calorie laden if that is your preference, and after that have something mixed with seltzer or tonic. Hey, in New York, you could have a "Skinny Girl Margarita" right?
Always have water on hand. Drink plenty of it on your visit to wash the sodium and calories through.
When dessert is the fare, share something. It isn't unusual for people to take bites and tastes. If you can control the damage to a minimal, you'll be okay. You'll be out of that environment, and away from temptation, sooner than later, and then you forgive yourself, get back to your regular routine, drink more water, forgive the number on the scale and don't obsess over it. You know how to do this--it won't be your last temptation (probably not your first either) and you've come so far in your weight loss efforts (congratulations) that this will come and go and you'll get right back to it. Don't be afraid to have a good time. Don't be afraid to eat/drink and enjoy the trip. I think you might be surprised, however, how your current lifestyle is engrained into your DNA by now...and you'll get through the trip practically unscathed.
P.S. I'm across the river from NY, so give me a wink and a wave when you're in town.