I live in San Diego and I am still thrilled to "visit", lol
In my opinion, San Diego has it all in one place.
Now, I am from Northern California and I love it up there. No Cal is gorgeous and the trees are magnificent.
But, if i could only visit one area? San Diego.
Depending on your budget, you can find nice places to stay in many different areas.
Obviously our beaches are beautiful. We have Sea World, a world class Zoo (just went last weekend), the Wild Animal Park, Legoland, Belmont Park (with roller coaster and wave machine on the beach boardwalk) and Coronado island (Hotel Del, etc). We have a happening downtown with great food, music, theater.
But we also have (within an hour drive)...casinos, mountains, and deserts.
I am a California girl, born and bred. I have lived all up and down the state. Santa Barbara is also beautiful (went to high school there), but not too much to do. Wherever you decide to visit, you will have fun. If you need anything, PM me.