Grew up in So. Cal. and two things I really miss are in n out and chick-fil-a.
I think for in n out one of the big draws is the freshness. Fresh hamburgers, you watch them cut the fries I love the shakes. But, keep in mind, they are fast food. That's what you get. They aren't gormet burger places, they are fast food burger places. Most days, I'd take in n out over sit down any day.
Some sit down places I'd recommend, otherwise, Red Robin's, Flakey Jakes (if there are any around), the previously mentioned Fudruckers. While I admit to late night trips to Fat Burger's, they were just too greasy for me. A bit or two goes a long way. If you wanted to get one to share and half it with somoene (for me, I'd only want 1/4), might work.