I just sailed on the Imagination 2/21-2/25 and it was great.It was the second time for that ship and they have made many new improvements! All the bedding and rooms have been refurbished, a waterpark was added and a "Serenity" area for adults only at the back of the ship is a wonderful addition. Both Cozumel and Key West have alot to offer...try Key West Trolley tour..a great way to see it... you can buy tickets that are fully refundable at this site
http://www.trustedtours.com/index.aspx. They are cheaper than booking through the ship and its the same tour. There is a nice beach in Cozumel "Paradise Beach"... it has good food, nice people, clean bathrooms and is free for the lounge chairs and umbrellas..a short taxi ride from the port. They also offer snorkeling, and other water amenities for a single rate of $10.00 for the day..can't beat that!!! Have a great cruise....