Lots of good ideas here. I have always believed that bananas are the cheapest health food in the world. They are around here, anyway. Since you live in CA maybe you have cheaper fruits.

Peanut butter is pretty cheap and has protein, but it also has lots of fat and doesn't fill you up. I lived on peanut butter for a year because I was poor and didn't have an oven or a stove.

Rice is cheap, and what is rice without beans?

I know this might sound old, but it's true...breakfast is the most important meal of the day. For me, if I don't eat a good breakfast it seems like I can eat all day and never really feel full. But if I eat a lot for breakfast and get really full, then I'm less hungry for the whole day. My breakfast suggestion: Frosted Mini Wheats. It tastes good and has plenty of fiber, and you can buy some generic brands for cheap.