Let me first say this cruise wasn't all bad, but it was definitely not a great experience. I also get the overwhelming feeling that carnival no longer cares.
We are a married American couple in late 20's. We have both been on cruises before, and even on carnival.
The Carnival Sunshine is a big boat, that is crowded, not a little crowded, but very crowded. You will not be able to do the majority of the interesting activities due to this fact. The layout appears to have been created by a complete retard. You can not travel from one end of the ship to the other on the majority of the decks that are not cabins (well you can, but it is for crew only).
Cabin was in the front of the ship, could look out onto the deck, never saw people there so it was like having a personal balcony.
fast and friendly embarkation, lots to see in the area like the national sea shore. the kennedy space center is also around as is some very nice beaches
Enjoyed cozumel, walked around on our own, got to see a lot of the island, it is really nice, just grabbed some beers walked down to the public swimming and enjoyed. There is a supermarket by the port which has the cheapest alchohal to take back to the states with, and it has food and drinks for the beach.
Super nice beach, fake but really nice and enjoyable. Really pretty, it is the american view of what the caribean beaches should look like. Heard that its super poor outside the beach, but the carnival police made a lot of effort to keep the locals away
Costa Maya had rain when we went, but we walked through the rain and went to the "city" wasnt really anything there, but it was pretty and interesting to see the dilapidated tourist area that was abandoned when they built the new one. Still fun and pretty, probably less so due to the rain.