I'm not in the planning for one of these but I can tell you a little about last years rally.
It was at Topsail campground in Destin, Florida. Their website is great and the campground was very nice, near the beach, concrete pads, full hookups, etc. We had a bunch show up as stated above - lots of food and fun. Weather in January is very nice. It's - I believe - in the first week of January, I have yet to see this years dates.
Post rally comments are in the original thread at te end. Check the link below.
2007 Florida Can Opener Rally