Red Tracton's is a really good restaurant. It's right across the street from the track. A lot of horse people go there. The downside is that it's really expensive. Here is their website: http://www.redtractonssteakhouse.com/
Another good restaurant by the track is Brigantine's aka "The Brig". If you go to The Brig you should go to the bar section rather than the dining room. The bar section is more casual and they have a separate menu where the prices are very reasonable. The most popular thing is the fish tacos. The restaurant is up on the hill right above the train tracks and overlooks the track (Del Mar). http://www.brigantine.com/locations_brigdm.html
The Brigantine is the place with Mahi Mahi...I had forgotten the name it's been so long