I finally moved into SoCal proper from the outside, so I've been accumulating food recommendations from friends.
I can speak and back up Dal Rae's. My grandfather lives in that area and used to take us all the time.
My current favorite place is this small little spot called Pasty Kitchen in Los Alamitos. They do, essentially, pasties, so handheld pot pies, but damn are they full of flavor (and don't skimp out on getting the gravy. I could literally drink the stuff). The place is old-school, and cash only, but the prices are incredibly good for what you get. Can't recommend it enough.
Big fan of KBBQ. I know it's not everyone's thing (and it definitely requires a group) but honestly my favorite food experience. If you're doing KBBQ, you really should head to Koreatown, and my personal recommendation would be Hae Jang Chon. It is definitely the more well-known and busier spots, but it's earned that reputation for being damn good. KTown also has Beer Belly, which is closing down soon but will still have a location open in Long Beach. Great beer selection, and the Death by Duck is, literally, to die for.
Finally, I'm a big fan of pho, and if you have the time, you might as well go to one of the best ones. Pho 79 in Garden Grove was given a James Beard Award, and it was well-deserved, as this place really did seem to pioneer pho in SoCal. (Though I will give a shout out to Pho Tasty in Artesia, which I've been going to for years and has always been quality).