ISO Cheap Lunch near High Bluff Dr, in North County
I like Champagne Bakery over in the Highlands Mall across the way (its right up by the movie theatre). Nothing spectacular, but I dig it for soups, sandwiches, pastries.
And, there's a Persian restaurant across the fwy behind the Jack in the Box off Del Mar Heights--I went there for dinner and wasn't bowled over, but I think they have decent lunch specials that would probably be worth trying.
Oh, and, this is a little bit more of a drive, but there is the original Spices Thai Cafe over just off the 56 (off Carmel Country I think?): 3810 Valley Centre Drive, Ste. 903. That place is always good.
Champagne is good, but I guess I wonder what do you consider "cheap"? In the mall across I5 is a really nice little Vietnamese place, Le Bambou. It's not pho, but more along the lines of city food. Lunches usually run about $6-10. There's also Elijah's deli next door. My wife went there for lunch recently and liked it (and she doesn't like a lot of Jewish delis.
There's Red Robin in the Highlands Mall also.
Nico's Taco Shop in the Vons' Shopping Center off Carmel Creek and Carmel Valley Rd is decent, won't blow your socks off but good enough for a Mexican fix w/o driving into Hillcrest. Souplantation is in the same complex as is Spices Thai Cafe. Pat and Oscar's is across the street near the Shell gas station.
Come on In! is on El Camino Real, south of the 56 in one of the office buildings before you get to Arroyo Parkway. I've only been to the La Jolla location, but they have good muffins, salads, etc.
If you're willing to brave the traffic on Camino del Mar, Pacifica Breeze Cafe and Americana are both good. Crepes and Cork is on Carmel Valley Rd, west of the 5. I haven't been yet but it's another option.
Sammy's Woodfired Pizza is in the Highlands Mall. I'd pick it over Champagne Bakery.
Spices Thai in the Piazza Del Mar shopping center is disgusting. Truly.
Villa Capri is probably your best bet in that mall, I've not been there for lunch but have had good dinners there.
You can also head over to Jimbo's in the Del Mar Highlands mall, they make good sandwiches and also have a salad and soup bar.