Last night at 22:18 hrs I heard Air Evac 50 lifting off from CTMC @ San Marcos so I turned the radio on 451.8625 CTCSS 114.8 and there they were requesting lon/lat of the call that they were responding to.
About 90 minutes later I also heard them call "on final, San Marcos" on that freq at the same time I heard them approaching the hospital.
I would say then that San Marcos Life Team will most likely be n the freq above. (As well as many others).