Taking a walk on the beach or in the Torrey Pines Reserve is very relaxing and close by. Take an architectural tour of the world-famous Salk Institute . Tours are Monday - Friday, at 11am and 12 noon. Visit Cabrillo National Monument on Pont Loma. Beautiful view, good historical presentation.
Military ships are open for touring almost every weekend in the harbor.
Check a local sandiego web site for info. Walk or jog or roller blade around Mission Bay. Roller blade rentals available on Mission Beach boardwalk.