Congratulations!
Hmm...how about taking the Ferry from the Embarcadero over to Coronado Island? You get a nice view of the San Diego skyline...there's a small shopping/restaurant area at the ferry landing on Coronado where you could get something to eat, or take a taxi to the Hotel del Coronado or the beach. The Midway aircraft carrier museum is near the ferry landing on the San Diego side.
How about taking a walk on the beach? Lots of nice beaches, including Coronado and La Jolla Shores. Mission Beach/Ocean Beach I don't think are quite as nice. There's also lots of beaches along Mission Bay - miles and miles of it. But the wave action in the bay isn't as romantic as that of the ocean.
There's tons of museums in Balboa Park, depending on what might interest you...art museums, Natural History Museum, Aerospace Museum, Museum of Man (anthropology), the Space Theater. Or there's lots of gardens to wander through (for free!) - the Rose Garden, Sculpture Garden, Botanical Garden...
Seaport Village is a nice open-air shopping district to wander around - lots of interesting little shops and some nice restaurants.
There's also the Old Town Historical District with various Old San Diego stuff, and Bazaar del Mundo has shops and restaurants.
If you enjoy hiking, visit Torrey Pines State Park (just north of La Jolla) - there's a lot of short (and I think relatively easy) hiking trails on the cliffs that are right along the coast, so you get some really nice ocean views. I'm not sure if the Beach trail is open these days or not. Torrey Pines State Beach is another nice beach area.
Hope that helps!
