Am wondering if any of you go into a deficit (weight lower than goal) before vacations/travel to mitigate weight gain? If so, how and how many pounds?

No, I don't. That would just mean I'd think I had license to eat more, plus I would feel hungry to start with.

What I do is plan to enjoy what I eat and to get plenty of activity. I don't plan to splurge, gorge, or eat with wild abandon just because I'm on vacation. I make the trip about the place, the people, and the activities, not about what I'm eating and drinking.

I don't because vacations are for fun and relaxing, so I don't spoil it by worrying about my weight or my diet. I'll deal with fixing my diet back up after the vacation. Of course, I don't go crazy, either. At the beginning of every meal I eat a salad or other vegetables to fill me up first so I don't eat as much junk. I also exercise every day of the vacation. I trust that helps

I agree with both replies above
Whenever I go somewhere for a few days, I simply make sure I don't go overboard with eating and I also make sure to do plenty of exercise. Even if it's just walking, as long as I move a little, worrying is not even an issue.

No, I just eat well and exercise as part of my travel.

I stay in hotels with gyms and plan running routes in places I visit.

And I eat a lot of seafood.

More often than not I actually lose weight while traveling because it's a lot easier to eat healthy when someone else is doing the cooking!

And I eat a lot. But a lot of stuff that is good for me. I have eaten hotels out of smoked salmon.