See the USS Midway if you are into that stuff. Most restaurants are closed but outdoor dining is available. If you are from the colder climate, that's what you want to do anyway.
Beach on Coronado is a must. Rent a bike and ride along the beach, soak up some sun. Balboa park's museums are fun. That whole area is worth visiting. Go up to Point Loma light house and the Cabrillo National Monument and get the almost 360 view of the ocean or bay. Light hike around the area. Spend the morning there, it's quiet peaceful. Depending when you come, it may be a bit cold in the mornings or even during the day but nothing a light jacket wouldn't do. Drive down and walk around the tie pools.
Rent kayaks (may not be open due to covid) and paddle around Mission bay. Its the back bay so no waves or man eating sharks
If you like the mountains, drive up to Mt Paloma and take a hike on any one of their hiking trails. You are in the clouds depending if we have fog or not. You can see for miles on a clear windy sunny day. Stop by Julian and get a piece of apple pie. They are famous for that. But its just an old tourist town in the middle of the mountain. Sure you have lots of them in TX.
How long will you be in socal? If you like nature, drive up to Palm Springs, 140 miles and take the Gondola up into 10,000' and take a walk to Round Valley through small streams and pine trees. You can see Mexico from there on a clear day. That's a day trip. We have done San Diego to Palm Springs and back in one day.