San Diego is one of America's finest cities and mine personally. The weather is excellent, always near 70 degrees F.
Don't miss Balboa Park and the associated Zoo... it's world class and given its due, will take almost two days. I could spen almost a day in the serpentarium alone.
Drive down the coast and visit Point Loma and the Cabrillo National Monument. The original Sea World is in San Diego and still the best in my opinion.
Take in one of the many Mission related museums for a flavor of the ealry Spanish settlements. The Star of India is the world's oldest seafaring ship. Built in 1863 at Ramsey Shipyard in the Isle of Man and very easy to get to.
Take a drive and catch the ferry to Coronado Island. Enjoy lunch in the Old Hotel Coronado.
So, OK, the restaurants are innumerbale and excellent... really good Mexican food, but drive down the short road on Harbor Islamd, just across the highway from Lindbergh Field (San Diego's airport) and have the world's best Margarita at Hamm's Lighthouse. Just back up the road a few clicks is The Boat House... a marina with really good seafood that was in the ocean a few hours previously... Think aobut going to Tiajuana... and then don't... a real depressing waste of time.
This doesn't begin to scratch the surface.. Welcome to the U.S.!