My sis and I took Elation cruise in April 2004 had a wonderful time. We are from Texas and even we found some of the woohoo whos from Texas stuff annoying. Please please don't think all of the Texans brought cowboy boots and stetson's on the cruise!
I agree with you on many points, especially that Progresso is a pit, if you don't plan on going to Meridia don't bother getting off the ship, that being said I think the town has the potential to develop into a more interest stop in the future. Cozumel is a tourist trap but to us that was part of the fun. Parents watch your teens here I took my 14yr old on another cruise that stopped in Cozumel and she was offered shots many times here. Belize is fabulous and the tender wait didn't bother me, it stands to reason you cannot take a ship that size over a reef and you can't unload 2000 people in 30 minutes, expect to wait and chill, you will get off the ship. FYI - if you go to San Pedro, Belize you cannot donate blood in the United States for a year.
Generally I think the people that go expecting to have a good time, have a good time, and the people that go expecting to find things to gripe about will find things to gripe about.
P.S. - I still miss Sonny the cabin steward!! and Stipe the Matre'd ( he has that Sean Connery, bald with a great accent carisma!).