Going into grammar for travel purposes doesn't make much sense, but there are a couple of points I think it's important to at least have a grasp of: Present tense regular formation, one past tense, basic sentence structure (SVO? OSV?) and how to ask questions. After that, vocabulary specific to certain situations like:
- Taking a flight.
- Ordering in a restaurant.
- Asking for directions.
- Checking in at a hotel or AirBnB.
- Any vocabulary specific to activities you're planning to do (hiking, museums, monuments...).
Hope it helps.