I took the same cruise two years ago, and would agree that Cozumel is your best bet. There are two places that I saw cruise ships docked - one is about 2 miles out of town and the other is visible from the main avenue that runs along the ocean (looks a lot like the Malecon in Puerto Vallarta). We were on Royal Caribbean so we were docked outside of town, but the cab ride is about $2.00 - there's a big duty-free store there; good for cosmetics, perfumes and booze.

I was a little hesitant to go too far off the "big" streets because I went into town on my own, but there is a farmacia at the cruise ship "center". Was able to buy factory sealed Soma (Somacid) 120 ct. for about $45.00. Asked for Ambien 10 mg, at first they said they didn't have it but then it was about $1 a pill, which is pretty much what it costs here.

My best advice would be to leave the bottle sealed and pack it deeply in your suitcase. When you get back into Miami, there are SO many suitcases coming off those ships, that I didn't see anyone have them checked. Carry-on bags, a percentage were checked, but I didn't see any suitcases looked at.