Kate, You’ll have a great Christmas in Playa Miramar. Let common sense prevail and you’ll be fine. It’s interesting how Mexico related news stories can get in your head and make you think it’s different now, but when you finally get down and settled in, everything is the same old calm peaceful Rocky Point.
Regarding driving, my advice is to drive during the day, come to complete stops at stop signs - even the hidden ones, get insurance, drive no faster than 25mph in Sonoyta, watch out for occasional potholes on the open road between Sonoyta and Rocky Point, and you’ll be good.
On your thieving question, advice here is don’t flash cash and fancy stuff and keep your house and cars locked up when away. Keep a critical eye on any unexpected maintenance/property mgr/utilities people who want to come in the house.
That said, have fun! Feliz Navidad.