Cozumel had a nice shopping area for the tourists. The locals were friendly. We booked a dolphin excursion and it was a wonderful experience. The trainer was experienced and gave us a great deal of information about the dolphin. There were about 10 people in our group and we each had individual time to interact with them. You will need to rent a locker for $4 once you arrive to store your valuables. No camera or jewelry are allowed. They will keep a form of ID until you return the locker key.
Belize was a tender port. The locals were not friendly and there isn't much to do once you get there. We did not book a shore excursion, but probably should have. We spent only a few hours in the shopping area before heading back to the ship.
We booked an excursion outside of NCL. We chose 'resort for a day' where we spent the day at Club Natale Bay Villas. It was an all inclusive package and we had access to the resort and the beach. Transportation was provided from the port to the resort.
The beach area is rocky and will require water shoes. However, it was very clean and you have the option to snorkel or kayak.
The pool area was very nice and the staff were friendly. We were served lunch and had access to unlimited beverages including alcohol.
The only downfall was that a couple of us had asked for snacks. They brought us chips and salsa and then informed us after the fact that these came at the cost of $5. We figured that since this was an 'all inclusive' package that the additional food selections would be free. We were wrong.