I don't about trainers in CA , I'm in NJ.
We researched a lot a found a trainer with a good reputation who is experienced with training and certifying service dogs. You need to find one that is willing to evaluate an existing dog.
It is very lucky if you have an existing dog that will make the cut and become a service dog in training. Until they do pass and are officially under training for tasks that mitigate disability they do not have privileges to go places where pets are not normally allowed.
Keep in mind the temperament testing and ability testing goes far beyond how well they know obedience. Keep an open mind and realize that even dogs that are top notch obedience trained still may not have that type of personality required to be service dog.
We are taking a gamble with a pup that seems to have potential. My trainer was very specific that most dogs do not make the cut. Our existing dogs are impeccably behaved but do not have the right temperament plus they are older and pretty formed in their dispositions. We have hopes on the pup but realize the outcome may well be an extremely well trained loved family dog that will make a great guardian , but may not make the grade to go freely in public as an SD.
Understanding that getting an already certified SD is impossible here ..there is a 2 year waiting list with all the agencies that provide affordable dogs..privately trained and certified run about 30K
Good luck. What type of tasks are you looking for ?