NEVER take your passport ashore. All you need is your sail & sign cars and a drivers license or government I.D. Don't need a copy of passport either although I do take one and leave it in safe aboard ship.
The Margaritaville in Cozumel has the 2nd best Margarita's after Key West. They come in a big mug too.
8 cruises so far and never a bad one. They are what you make of it. Just have fun.