Welcome to the forum. I am a native of San Diego and have fished the area extensively. But never with a fly.
Started that after I moved to Utah a dozen years ago. Not familiar at all with guides for the area. What your options will be I am sure depends on the time of year you go. Lots of saltwater action, and some good largemouth bass in fresh water. Trout fishing is not very good there. But the Sierras have some great areas for that just a little north. Now if you plan a trip to Yellowstone or to Utah, let me know. Enjoy the forum. Some great people here and I am sure someone will chime in and can give you some better direction for So Cal. Good luck!