I'm in Texas so I can't recommend a trainer in CA, but ask around. Ask your vet, neighbors, etc.
The first trainer I went to was recommended by our vet. She was a very nice lady but a horrible trainer. I went to only 2 classes with her.
Then I spent quite a bit of time doing internet searches for trainers in a 3 county area. I found one who I am thrilled with in the next county. So I have a longer drive, but it is so worth it. She has been training for a while, she also trains and shows her dogs in agility (which I want to do). Her & her partners have a fairly large building. They also do grooming, boarding, and doggy day care. Mine goes twice a week to get the additional socialization. There is also another GSD in our training class, which is nice.
So finding a trainer on the internet is not necessarily bad, but if they aren't what you are looking for then walk away and try another.