lunagirl,
We've been to Varadero in early December. The weather was fine, temps around 28/29 during the day. At night it got a little cooler down to about 21, so you might need a light sweater.
The water was cold at this time of year. The ocean was a little warmer than the pools. We spent most of our time in the ocean. The pools were freezing cold and empty.
It's hard to predict what the weather will be like because every year is different. This year there is supposed to be more tropical storms than last year which might make it a bit cooler and rainy.
I wouldn't say don't go at that time of year, but go expecting it to be a bit cooler than in the summer. You will still get a lovely tan and still be able to swim in the ocean.
Hope this helps.
Where were you in Mexico, and what happened?
Heather