I used to. I've drive to the 'end' of Angeles Chrest Highway, meaning the point where they stopped plowing it and then take off cross country skiing. It was a very nice bit of excercise, about 3 miles of rolling terain to Islip saddle, then a long gradual climb. I'd just go until exhausted and then turn and have a long easy gradual downhill and then I was rested enough for those 3 miles back to the car.
It was sort of funny as I'd ski in shorts and see others out in down from head to toe.