Perhaps a rescued Golden Retriever? Or Golden mix? While they are not supposed to be protective per se, most will bark if something is wrong. My first dog was a rescued Golden when I was a teenager and she was a great dog. She was very athletic and loyal, she was active when I wanted to do something active but also could relax and "hang out" with me if I wanted to do that. She taught me a lot. We dabbled in many dog sports and she did pretty well at them all. We did lots of agility, obedience, animal-assisted therapy, a little bit of rally, a flyball class, lure coursing, some freestyle, skatejoring, carting, weight pull training, tried dock diving, even Earthdog (above ground version). My Golden did "protect" in that she would bark if someone came on our property or came to the door and she would not let people in the house uninvited; and she also did "protect" me from suspicious people several times in her life (by standing in front of me solidly and barking until they left) even though she was a very friendly dog (a therapy dog) and loved people.
Here are some rescue groups I think are somewhat in your area:
Welcome to Southern California Golden Retriever Rescue Southern California Golden Retriever Rescue
Retrievers and Friends of Southern California
Homeward Bound | Golden Retriever Rescue & Sanctuary in Elverta, CA
OCC: All Retriever Rescue