Cheap eats in Davis for dinner?
Another thing to add: 4/19 is Picnic Day. Which is, presumably, why you'll be in Davis.
Stay far, far away from campus. The farther, the better. Sam's will be a nightmare. Downtown Davis will be slightly better, but not much. If you really need to escape the throng, try Taqueria Guadalajara, on Mace. It's better than the one on Anderson. [http://daviswiki.org/Taqueria_Guadalajara]
Or, head to Symposium for pizza. Best pizza in town. And wave to me, because I live across the street! [http://daviswiki.org/Symposium] If you get take-out, you can walk two blocks down Chestnut and eat your pizza in the park. It's less stifling than the restaurant itself.
My first rec would be Davis Noodle City. They make their own noodles. It's very fresh and delicious. Small place, though. Huge portions for $5-$7. (http://daviswiki.org/Davis_Noodle_City)
If you're wanting Mexican, El Mariachi taqueria is very good. (http://daviswiki.org/El_Mariachi)
I haven't tried Burgers and Brew yet, but people like it. It'll probably be crowded, though. (http://daviswiki.org/Burgers_and_Brew)
Avoid Bistro 33. Others will probably recommend Sophia's for Thai, but I much prefer Thai Recipes across the street. (Although Davis Noodle City knocks them both out of the water.)