One of my favorite stops on the way into the park is the Costco at Harbor & Orangethorpe in Fullerton. The food court is on the outside of the building so I don't think you even have to be a member to eat there. ( they've never asked to see my card ) They have a great hot dog & drink combo for like a buck-fifty. You're not going to beat that anywhere. They also have pizza for $2 for 2 slices, chicken bakes and turkey wraps & a caesar salad frozen yogurt & ice cream.
There is an In-N-Out in the same shopping center and the character warehouse of discounted Disney stuff is just on the other side of Orangethorpe.
I go to the park via the 57 fwy and Ball ave. so there are lots of fast food places along the way. Carls jr on State College just north of Ball is another regular stop. There's also another McDonalds on Ball before you get to Harbor, it seems less crowded and cheaper than the one on Harbor.
If you're interested in some other restaurant or fast food place just go to their website and check out their location finder. Enter 1313 Harbor blvd Anaheim as your start address and you're all set. The ZIP is 92803 if the site gets picky. Denny's and Hometown Buffet both have locations not far from DL.
It's definitely worth the drive for some decent food.