We were at the Hotel Del Coronado for a week (business conference that I added onto) -- Spend some time on TripAdvisor as you plan.
DH was on his own a bunch through the week. He loved the USS Midway Museum (he's a history buff). He also played golf 2 days (while I was in session). He also enjoyed the Air and Space Museum.
We took a whale watching cruise on a sailboat -- included admission to the maritime museum as well (on the HMS Surprise from the Master and Commander movie). The whale watching was on a sailboat and was a great experience:
https://nextlevelsailing.com/ They had a guarantee that you'd see a whale -- and we did, even out of season! The captain of the cruise had been an extra on the movie and had a number of stories about the filming.
We had a great meal in La Jolla - Duke's -- it was wonderful, and we reserved the patio overlooking the water.
https://www.dukeslajolla.com/menus/dinner/
On Coronado Island, we had a great meal at the Bluewater Boathouse Seafood Grill:
https://www.bluewatergrill.com/locations/coronado.php
We also ate at Leroy's Kitchen and Lounge (farm to table) on Coronado, which was really good -
https://bluebridgehospitality.com/leroyskitchenandlounge/
We didn't go to San Diego proper much, but enjoyed the Zoo. We also enjoyed the Balboa Park museums -- they have a whole bunch of smaller museums that we tried to do all in one fell swoop -- they started to all look the same at one point. The model railroad museum is amazing.
We'd gotten the Balboa Park Explorer Pass which was good for a week and included the zoo and all of the museum admissions (except the Midway). You'll need to calculate if it makes sense for you before buying it, though. You may be able to get a Groupon for it.
https://explorer.balboapark.org/
We did rent a car, because DH was on his own so much. It was helpful. If we had a few more days, I probably would've included a day tour to Tijuana.
Enjoy!