Sean,
My buddy and I went to Key Largo for a week of diving at Christmas 2003.
We ended up flying from the west coast US (San Jose) to Miami on Christmas day and returning on New Year's Day. My buddy booked those days because they were significantly cheaper than other days. As expected, traffic Christmas day was pretty light at the airports. I was concerned that it might be ugly traveling on New Year's Day, but it actually worked out just fine.
We were not able to book into the place we have used before, and they were much more expensive than on previous trips. My buddy ended up booking us into the HoJo's in Key Largo, and I won't stay there again unless we have no choice.
We dive with Horizon Divers and they were able to accomodate us and all our requests. We did Wreck dives and night dives with no problems. Most of the regular daytime dives were pretty shallow, but we didn't request anything on those days. We saw a lot of fish, and we had a very good time.
We are not party animals, so we didn't explore the night life above water. We ate at local restaurants and spent mellow SI's. We did meet Dick Rutowski at a bar right by his shop.
There was a nice fireworks display down near Pennekamp, but we watched it from the Motel grounds a couple miles away. (my buddy is a real stick in the mud sometimes when he gets tired, and he gets tired easy)
The water temps were a lot lower than on previous visits to Key Largo. Water Temps ranged from 73 to 68 degrees F. I had to switch from the .5mm wetsuit to a 3mm wetsuit when it got below 73 degrees. With the 3mm wetsuit I was fine.
The Fish House is certainly one of the most popular and best known restaurants in the area, and worth a visit.
Enjoy! I wish that I could be there too.
Wristshot