We’re in SW Virginia. When D comes home in the winter I’m bundled up and she’s in short sleeves 
She’ll be sweating in San Diego! I think last year’s San Diego weather looks perfect (our 2014 Christmas vacation in Florida also had perfect weather).
Taco Tuesday
Coincidentally, I’m re-watching my way through some of Billy Wilder’s films with D. “Some Like It Hot” (1959) was filmed at the Hotel Del and a funnier movie is hard to name.
Thanks, @GladGradDad for the info about Rubio’s sustainable practices but D’s a teetotaler. 
And, on her behalf, here’s a plug for the Birch Aquarium at Scripps:
http://aquarium.ucsd.edu/Plan_a_Visit/
Apologies if that turned out to be a repeat.
Just wanted to add that I’ve been fascinated at the varying character of beaches in San Diego. Some upscale, some more family oriented and other varients besides. S has made it a passion to find all sorts of interesting places for fish tacos, and Mexican as well as Asian food. His favorite is at Ocean Beach.
Had never heard of Rubios, and happy to see they are in Phoenix, so will look for them when there.
Those tacos better be darned good to justify traveling 2500 miles.
No but the weather and location makes them taste pretty darn good. Actually the best fish tacos I’ve had was in Big Island, but I’m not going back there. My husband does like the drinking water there.
Rubios is a chain. The first one is the one in Pacific Beach (San Diego). You can find many locations. Good stuff!
For a long while, my son’s dream is to operate a taco stand on the beaches in S. CA, preferably Newport Beach.
Santa Fe is magical at Christmas.
San Diego is not that magical at Christmas away from downtown, which was fine by us last December since we celebrate Chanukah. It was actually a relief to escape the extensive decorations seen back in Chicagoland. We were amused by the number of inflatable Chargers instead of Santa and Frosty snowglobes in neighborhood yards (big game while we were there last year).
There are some lovely decorations, however, including one block on Garrison in Point Loma where every house is extensively decorated with lights, animated scenes, and more. I also read that there’s another area where the neighborhood does luminaria on Xmas eve.
I haven’t been to San Diego or Miami so I am voting for New Mexico. You can see Albuquerque in a day or two and Santa Fe and Taos are wonderful. Taos pueblo has its big festival on Christmas Day where they do the deer dance ( I believe).
All the pueblos are different and worth visiting but the wonderful handicrafts are quite expensive. I love the tour at pueblo Acoma where North Americas oldest city is ( first settled in 1100 AD or thereabouts). After the tour of Sky City, you can climb down the mesa instead of taking the bus. It’s not that hard. And pretty cool to be using hand and foot holds that have been there for hundreds of years.
NM in the winter can be provincial and you may find things closing earlier than you’d imagine, so plan ahead.
Abiqueue and Ghost Ranch (home of Georgia o’keefe) are wonderful but the best place of all, to me, is Chaco Canyon. It is a national historical park and has a long unpaved road that reaches it. If you can manage that, you will be rewarded with Anasazi ruins from the height of their civilization.
I’ve been to this area three times in February and it was never too cold during the day. Sunny, and from the 60’s to the 40’s.
hmmm, New Mexico is gaining in support!
Abique ghost ranch is amazing if you like hiking. But it’s a long drive from Tao, and other places you may consider staying. Taos was fun in September, but I’m another vote for San Diego. But consider yourself better off than me in any case. I will be in Gettysburg PA, where there will be pretty much NOTHING going on during that time. Smile and nod, smile and nod. (It’s a family get together trip).