A valid US passport is required. You do not need to be vaccinated, nor have a COVID test, to enter Mexico.
NO! This is one of our favorite things about this place...no reservations required! Restaurants are all first come, first serve, but we've never had a problem getting in anywhere.
Yes. You can find the dress code at https://en.valentinmaya.com/restaurants/dress-code-required/. In general, just think about long pants for men at night with a button down or polo shirt and nice sandals. A couple of the nicer restaurants require closed toe shoes for men - think sperry's/loafers. For women, go with a dress or capris and nice sandals. No beach flops is really the main thing.