Miami is not my favorite city. I stay in Ft. Lauderdale prior to the cruise for a few days (sometimes a week) and shuttle in the day of the cruise. The best is to go back to the airport (FLL) and get checked in there then take the Carnival shuttle. It's cheaper than Uber or a taxi.

I like grand Turk, especially since Carnival set up a charity for the stray dogs. I've never gone on an excursion there, but I like the beach and hanging out at the giant Margaritaville. The pool is amazing and it's a great place to people watch. Some of the chairs and umbrellas belong to the cruise port and are free, however, they are mostly the ones farther away from the water. You can rent a nice cabana close to the water for about $30. Bring cash because if you use your credit card, there are some pretty steep fees the restaurant charges on top of very expensive food.

San Juan is just beautiful. If you can, take a walk around the entire city and visit the old forts. The views are breathtaking. There's a Starbucks just up the street from the pier and if you keep walking up that same street, you'll see hand made crafts, cigars and such. Take a peek into Eclectica for very reasonably priced jewelry and other beautiful goods from around the world.

Don't count on much at the cruise port in St. Maarten. There's a small market place and a jewelry store, but that's about it. You're better off to hop into a taxi and go into town for better shopping and access to restaurants. The beach at paradise island is an adventure. You're taken there in smaller boats. Otherwise, I just stay on the ship at this port. If you rent a car, which I did one time in St. Maarten, be aware there are a lot of round abouts (rotaries) that are totally confusing. Even though you can drive in a complete circle around the island, the round abouts got me lost and I almost missed the ship leaving!