Food near Berkeley Greek Theater
The area near Euclid and Hearst has some ok options, and is the closest dining district to the greek. If it's summer, you should be able to find street parking around there. Top Dog, Bongo Burger, and Aki Japanese all serve decent, inexpensive food. For good, inexpensive food, you'll need to travel to the Gourmet Ghetto or Downtown where you can eat at Cheeseboard, Gregoire, Bobby G's, Mint Leaf, and others. This would mean either a longer walk (turning a 5 miniute walk into a 20 minute walk) or parking twice (though, again, parking isn't bad during the summer). It all depends on how important good food is to you.
2154 Center St, Berkeley, CA 94704
1513 Shattuck Avenue, Berkeley, CA 34957
Aki Japanese Restaurant
2505 Hearst Ave, Berkeley, CA 94709
The Greek Theater is in the University district, so a lot of the food you'll find around there will be burritos, hoagies, pizza, and hot dogs. On Telegraph Ave. you can find some good pub food. There's also a good veggie restaurant there on Telegraph.
Sorry I don't have any names. I lived in that area back in 1998.
You could walk down to Euclid and find something nice, but it would take you about 25 minutes or so while Telegraph would only take about ten.