From what I found during my trip the first week of December is that the pools are heated. If the wind is blowing it may be a little cool. We had perfect weather. Bring layers/sweater for nights. I did and didn't need it, but was nice to have if it was necessary.

I posted my trip report and picture link here if your interested.

February is much cooler than December.

But it will still be nice. I would go

It was plenty warm in Cabo during the day for sunbathing and the pool or beach (my one trip there was approx that same time of the year). It only felt a little bit cool to me really early in the morninga couple days, or sometimes in the evenings if I was eating dinner after dark in an open-air patio restaurant. Even then a very lightweight linen jacket was all I needed.

I second what suze said. Take a light jacket for the evenings, but the days average in the mid-to high 70's. I found the water a little too chilly for swimming in February.