Every year, Balboa Park hosts a terrific holiday event. December Nights is the first Friday and Saturday of December, from 5-9pm. All of the Balboa Park museums are open and free. There’s music at the Spreckels Organ Pavilion and elsewhere throughout the park. There are vendors of all types. The Spanish Village has all kinds of art for sale. It’s really cool.
My favorite part has always been the International Houses, though.