For Delta, go to the customer service counter in the international terminal, they will have you pay your taxes, and give you a paper ticket/receipt with "JSA" on it. Then go to the gate for check-in. They will give you trouble at the gate if you show up without paying the taxes first at the international service counter. (Do not check-in outside of security, they do not know how to handle jumpseaters intl'). Hope this helps. I went down to CUN on USA3000, easy again. Came back on Ryan (Funjet). I would recommend this, as I paid nothing on Ryan, and was treated like royalty (pre-boarded while they were still doing the aircraft security sweep!). Charter is the way to go, it's just figuring out their schedules which is a pain in the butt. Good luck and have a blast in CUN!