Old Town in San Diego has a LOT going on, including many yearly festivals. You can find shops selling kitsch, pottery, beautiful items hammered from tin, Tibetan goods & clothing. At one end is a large square park surrounded by a few restaurants & museums. My favorite shops are the San Diego Mineral & Gem store and South American Imports.
If you're into ghosts, there's a haunted ghost tour as well as the Whaley House, one of the most haunted homes in the U.S.
San Diego's only African museum can be found here run by a professor named Chuck Ambers.Check out the African & black American artifacts & learn about black Americans who took part in the founding of San Diego. If you go, make sure you have a few hours because he has a lot of stories to share!
For eating, you have many choices. My favorite is Berta's South American cuisine located in a little white house. Gorge is the server and if you have a couple bucks, wave down the occasional street musician and he'll play you a song while you eat.
At Fiesta del Reyes, there's a stage where you can watch traditional Mexican dancing on weekends and enjoy a mojito on the large outdoor patio, no indoor seating. There's some more shops around there to check out!
Finally, there's the remodeled Cosmopolitan hotel & restaurant. It's made to look like the early 19th century and the food is pretty good. Watch those drinks though, the recipes are from the time period and apparently, folks drank it strong back then!