If your profile is up to date, you're certified under a year and have under 25 dives, with PADI as your cert. agency, so I'm guessing you're OW cert.d but not AOW or Nitrox.
In December, some of the northern Caribbean will have chilly water. If you dive in a a wetsuit all the time anyway, this is probably not an issue. If you are like me, naturally insulated, and prefer water 76+ (my personal range) so you're comfy without a wetsuit, then southern locations like Bonaire start to look better.
I think a group trip this early in your dive traveling is a good idea. A few thoughts:
1.) Cozumel is loved as a budget destination with good diving and a number of very reputable op.s. But dives tend to be deeper than 60 feet, if that bothers you, and drift dives (which a number of us enjoy; some people don't). I've been a day one January and I think the water was around 76 degrees. With the caveat that you'll probably dive deeper than you're used to, this could work.
2.) Key Largo is normally what I'd recommend, and in the U.S. less need of a group for comfort. But I don't know what conditions are like that time of year, and water would be cool.
My trip report from Sept. 2013 to give you an idea what to expect.
3.) Bonaire - shore diving with a group familiar with the place can be wonderful. I've been 8 times; 1st 4 with a group, next 3 with family/friends or a friend meeting me there, solo last time.
A number of group trips to good places at good prices book up faster in advance than this.
It's possible to travel alone and have a good time. Especially if you're been outside the U.S. before.
Richard.
