Oak Glen is a prime Southern California area for growing apples. It is located in the hills of the San Bernardino mountains, about an hour's drive from Palm Springs. We like to drive up there every fall and buy cider and apples. The other apple area is up in Julian, which is in San Diego county, the other direction. We don't get over there as often.
We first stopped at Riley's Farm. Riley's Farm is an authentic old farm, with sheep, a bakery, a house, and they grow apples, strawberries, and another crop, which I didn't see. They have tours for schools. I know our first grades have always gone up there. If you go, get there when they open (10 a.m.), otherwise it is quite crowded.