I lived in San Diego for 6 years, the latter part more inland by SDSU. We moved away in 2003. Things have changed a bit in 9 years, sadly some of the places I used to haunt have closed. I don't know that many places on the coast, but I do love:

Bronx Pizza
111 Washington St. San Diego

A bit further out by SDSU
Carne Asada anything
Trujillo's Taco Shop
5119 College Ave

Worth the drive to the local mountains:
Julian Pie Company
2225 Main Street
Julian, CA

Local So Cal chains I love:
Pick Up Stix - Gotta try the House Special Chicken
Rubios's Fish Tacos

Oh my, my stomach is growling just thinking about it.

If you're in downtown Carlsbad, I'd stay away from Norte (used to be Fidels) unless you like Americanized Mexican (some people do, not knocking it). I like Las Olas better. Teri's Cafe (2 locations in Oceanside) is good for family style Japanese - ramen, udon, some sushi, etc. They make their own noodles. Mikko (Carlsbad Village Drive near the freeway) is very family friendly sushi, but Hon Sushi in Oceanside is better quality. Lots of pho places in Oceanside - I Love Pho, near one of the Teri's locations in Oceanside is pretty good.

Also in Oceanside is Bull Taco (offbeat Mexican-ish), Panca (Peruvian), and Guahan Grill (Guamanian), all very good. I live in Carlsbad, but for local casual ethnic, I always wind up in Oceanside for some reason.

Wow thanks for the responses. We are actually leaving tomorrow at the crack of dawn. I hope to be able to use at least a couple of these suggestions, definitely ramen. I really appreciate your advice.

If you are visting SoCal you have to get a double-double Animal style at In-N-Out Burger.

Fries normally come soft/lightly fried. Ask for fries Light-Well if you like them crispy.

For the full off-menu SoCal local experience order a neopolitan shake.

In-N-Out Burger
5950 Avenida Encinas Carlsbad, CA 92008