If we are down there for dinner, I usually insist on eating at Fillippi's Pizza Grotto on Kettner. It's an old -fashioned (because it survived) Italian restaurant behind the market place. It just reminds me of a lot of the little family Italian places we ate at when I was a kid and then when we lived in San Diego. Most of the other Italian food places in "Little Italy" are fancier finer food places. Most of Little Italy was eliminated when I-5 was built.
I guess if I was to make a recommendation on food for San Diego, it would be to try one of the ethnic places that you might not be able to find in Indiana. Middle Eastern, Asian, that kind of thing.
For Mexican, We like Old Town Mexican Cafe, I usually get the ribs. NOTE - These are Mexican style ribs and not like you get in most parts of the states. Most of the places in Old Town are pretty good, ranging from good "American" style Mexican food to good Mexican Mexican food. Try Mole Poblana or Mole Enchiladas if you've never had mole. You need to get recommendations. Old Town can be a bit of a tourist trap, but it's kind of fun to wander around in and shop for souvenirs. Neither Ma Danby or I are drinkers and we live about 2 hours (good traffic) out of San Diego, so I definitely wouldn't try any of the big drinks.
If you can get it, Anchor Steam Beer, Anchor California Lager are nice beers, not the average American horse piss. Steam is really nice on a cold night. Not sure I could recommend any Mexican beer.