I live in the San Diego area but I do all my own work with exception of alignment below. That said, there are many good shops around and one already mentioned European Motorsport was used by a friend of mine and he had varying results with his 914, 911, and 944. I have no experience with them and have never been there.
I have bought parts from Black Forest and been there many times, good people, and one of the best engine people in SD, Mark Kinninger. The friend I mentioned before had work done on his 914-6 there. Another mechanic, Steve Groskemper used to, or maybe still races a 914, I don't keep up with the race folks.
There is Mekellos in Escondido with likely the other best engine mechanic in SD area. Good shop, as I've said I do my own work, but I know these people and been there many times as well. They have done 914 restorations and know 914's.
Vollig on Mirimar Rd is a good Porsche shop and I like the people there but not sure about 914 work. I had a 911 aligned there. Owner is a racer and grew this business from his garage.
Also in Escondido is Renaissance is a small one man shop. Joe. I was to an open house there and it was quite impressive, but I am not sure he is a 914 guy.
As with most anything with the word Porsche, prices can vary greatly. I'd suggest visiting each of the shops and find one that feels right and can give you a good solid estimate of the work you need.
PM me if you like and I can fill you in more.