The biggest park in the city with gardens and museums including the San Diego Zoo.
A big food court with a variety of shops, restaurants, and bars in what used to be the old US Navy base.
A giant aircraft carrier turned museum docked in the SD harbor. The harbor drive there is nice even if not visiting museums. There is a waterfront park with lots of interesting ships and boats docked.
A pretty overlook at the tip of Point Loma protecting the SD Harbor. A national park pass or military ID will get you in here to check out the view and lighthouse.
A hilltop overlook above La Jolla with spectacular views up and down the coast. The park at the top is a memorial for Veterans with little plaques telling their stories.
The bluffs at Torrey Pines are a great lookout point. Here there is a takeoff and landing point for gliders riding the wind where it rises up along the cliffs from the beach. Super cool thing to watch.
In Encinitas, you will find Swami's and the meditation garden. Swami's is a legendary surf spot with great views from the park above. There is a wonderfully maintained garden free to enter if you are quiet.
I haven't been to Legoland since I was a kid but I remember it being the most fun amusement park ever.