I am not an expert on this subject, and I'm going to assume that you're traveling on a U.S. or Canadian passport so you won't need any visas. You're going from Home->Mexico->Belize->Guatemala->Mexico->Home. Traveling from country-to-country should be no problem. You check out with one country and check into the new one, pay your entrance and exit fees, etc. One bit of advice, make sure you have your return ticket home with you, they probably won't ask for it, and they probably also won't ask you to prove that you're not indigent (by showing them cash dollahs either) but better safe than sorry. The only hangup might be in your return home from Mexico-don't panic- the airline you flew in prepayed your taxes, and you had to gave up proof of this (payment)when you left Mexico (-your tourist card). I've never had a problem with this at the airport, but I had a had a friend have to dash over to the Banamex and pay the $25 fee (you can't pay it at the airport) and she almost missed the plane. In theory, the tax you pay is supposed to cover you for 30 days, but she had a bad experience. Maybe her experience was unique. You should explain to your airline representative what you want to do and see if it is a problem. I hope this all makes sense.