Contact the villa owner or rental agent about how many hours the pool heater will be set to run. They usually run as little as 8 hours and as long as 18, but I haven't had a rental where it was on 24/7. If they only offer 8 hours, I'd give it a pass. Many do shut off automatically when the outside air temperature hits 55F, but not all. (Solar heaters won't do much good overnight, but will keep the water circulating.) Electric and gas will heat the water faster than solar heaters, especially in the short December days. Gas is faster than electric. If there is a pool cover, and there should be for most regular sized pools, use it. It helps keep the water warmer overnight so it will warm up faster the next morning.
I use the pool about 50% of the time in Dec/Jan when I'm down there. It really depends on the weather, which is problematic. Is that worth it to you? and is there an outdoor spa that you'd like to use? That alone may be worth the pool heat cost. I've also found most of the good rental agents do extend the hours the heater is run and will set the temperature higher to keep the heat on so their guests are happy.