We enjoyed a 6 night stay at the Temecula/Vail Lake KOA over New Years.  It's a great, yet remote location for exploring the Temecula wine country and a good jumping off point for some fun mountain biking. 

The KOA was pretty crowded during the time we were there with lots of families, kids on bikes, dogs, etc.  We didn't mind but if you are looking for solitude, this may not be the place for you.  The amenities are very worn. Bathrooms looked like they'd not been updated for a long time and decaying recreational facilities like the putt putt, motocross and pool area were unusable.  There was, however,  relatively new pickle ball courts which made it look like the owners are trying to maintain an old and very large property.

Staff was friendly and helpful. There were a number of activities for the kids too.

Overall this was a fun place.