We love Balboa. It's a beautiful, large park, with museums, historic sites, and trails. It's also home to the San Diego Zoo.
Coronado Island is a resort town located across the bay from downtown San Diego. It has wonderful hotels, shops, and beaches. Having a cocktail along the water is not inexpensive, but it is memorable, particularly at sunset. Fun fact for all of the geography folks: Coronado Island is not actually an island, but a peninsula. But don't tell that to the people there; they will not care. At all.
We recommend walking along the beach at Torrey Pines State Park. It runs along beautiful cliff faces, and is home (perhaps unsurprisingly) to the Torrey pine - a tree found nowhere else on earth.
We are (proud) members of the San Diego Zoo. It's centrally located in Balboa Park. We recommend the meerkats, tapirs, and giraffes. The capybaras bring us no small measure of joy as well.
This area houses our rehearsal dinner space, Stone Brewery, but it's well worth taking a larger look.