Hey Adam --
I think OC'ers split between this board and the L.A.-area board (loose interpretation of "L.A. area") in hopes of getting more responses over there. We're kind of in limbo!
Sounds like you're looking for good CASUAL stuff. Here are a few places you might like:
TACO MESA -- high-quality, non-boring Mexican stand with a good vibe. It's been written up all over the place, but it's still very reasonably priced. On 19th Street in Costa Mesa, among a few other locations.
HARBOR HOUSE CAFE -- has a great BIG burger along with other coffee shop fare and is open 24 hrs. for late-night excursions. I've been to the one in Dana Point, and late at night the back room has lots of atmosphere (wood walls covered with tons of photos).
MOTHER INDIA -- Popular Indian place with great service in Costa Mesa on Bristol. I think the chef came over from a fancier place years ago and really knows his stuff. I must say it's been inconsistent a couple of times lately, though (alternately too salty and too bland); hopefully just a temporary problem.
DORIA'S HAUS OF PIZZA -- Gotta love that name. Cheap family-style Italian, really casual. But go for the pizza over the typical red-sauce entrees. Chewy crust and very cheesy. On Harbor in Costa Mesa.
One place I love, but it's more chi-chi, is Ramos House Cafe in San Juan Capistrano. It's only open for breakfast and lunch (and be warned, Sundays are only for a pricey brunch, I THINK), but the atmosphere is truly lovely -- outdoors under a large tree. The food is creative and delicious. It's fancy and simple at the same time.
Sorry to ramble. If these aren't near you, re-post, and I'll try to check back.
Hmm, it's been about two years since I lived there, so not all these places may be there.
I'll second the TACO MESA recommendation. It's one of the places I truly miss. The Mission Viejo branch is as good as the Costa Mesa one, though not quite as much character.
There's a superb sushi place down by Yaohan in Costa Mesa. Can never remember the name but pretty sure it starts with an A. Think it was also discussed on the L.A. board a while back.
There wass a Jewish deli in Laguna Hills right by the 5, but tucked a little out of sight (by the Laguna Hills City Hall). Real stuff -- plates with two kinds of pickles and cucumbers, great matzo soup, proper pastrami, etc. I think it's run by Russian immigrants.
Black Sheep Bistro in Tustin had wonderful southern French food.
Steelhead Brewery in Irvine, right across from UCI, made decent food and good beer.
Also in the Tustin area were a couple of Indian groceries that had buffet counters and made dosas, etc. to order. Used to go about once a week for lunch.
Trabuco Oaks Steakhouse in Trabuco Canyon. You can guess what it serves.
I know it's not a restaurant, but one of the best meat markets you could want was El Toro Meats on El Toro east of the 5.
Little Saigon has more places than you can count.
Hmm...guess there aren't any other OC people on these boards. Well, I haven't lived there in 7 years, but if you like Asian food, check out Little Saigon in Westminster. Basically, drive down Bolsa(or First, if you're coming from Santa Ana) until you hit a whole bunch of stores and restaurants with Vietnamese on the signs.
For more chi-chi eats, go down PCH around Newport and you'll pass some upscale places. I've heard raves about Five Crowns and Las Brisas is supposed to be really good, too.
I was just a high school student when I lived there, so I wasn't exactly busy checking out the local restaurants. =)
For burgers(and especially their amazing cheese fries), I'd suggest Island's. I think it's a chain, but there was one near my house in Fountain Valley/Huntington Beach. Besides really good Vietnamese noodles, Island's chedder fries are the one thing I crave most that I can't get outside of OC.
Hope this helps. :)