As you can see we have done Carnival alot and the Fantasy 3 times in the last 12 months.
All that said, the best tip is to keep your expectations realistic.
We love Carnival...but I will be the first to tell someone it is not 5 star. However, you don't pay 5 star rates either and you will definately get your money's worth.
The New Orleans terminal is only a year or two old and is a nice addition to the port. The folks there are friendly (HEY ROBERT!!).
Cozumel is also my favorite port. Very safe, tourist friendly and lots of fun. There is always transportation available. WE joke that there are more taxis than sand.
If you want to swim with dolphins, you can book it independently and save some bucks. You go through Chankanaab Park.
If you want a free beach resort (no entrance fee for the use of the lounge chairs, clean restrooms, internet at the bar, umbrellas etc) we go to Paradise Beach. All they expect is that you eat/drink while you are there. They do offer an optional wristband for $9 if you want to use the water toys like kayaks and snorkeling...but the snorkeling from the beach (at any resort) is not good in Cozumel. It is ok for beginners. Some parents use it to introduce their kids to snorkeling because it is inexpensive.
You really need to go to the reefs if you are a die hard snorkeler!!
You can book that independently as well and save some money.
All of these independent recommendations of course are only if you feel comfortable doing that. Some folks prefer to go through the ship and the ship does indeed offer all these excursions!!
If you are on the 5 day cruise, you will go to another port. It used to be Costa Maya...but hurricane Dean changed that for several years.
If you go to Progreso, there is not much there. Again, I have heard it is pretty user friendly. We are headed that way next month on the Holiday. Complaints I have heard is lots of seaweed in the water and aggressive vendors.
I believe that Big Tex will be your CD. I believe he and his wife are on the Fantasy until the end of January. He is super nice. Be sure to do the Mardi Gras Pub Crawl. We brought our own "flashy beads" for the occasion.
Personally, I feel like the Fantasy is in need of a drydock. They work hard to keep her looking good...but she does take a lot of abuse. When we were on her in August, she was still ok...but was starting to look a little tired. Nothing that will influence your cruise...just a hint of it here and there.
She goes in for the Waterworks refit the end of 2008...so I would imagine that is when they will freshen her up as well.
Staff and crew were friendly. We have always had a good time.
Hope yours is a good one as well!!