Looking to buy a car, help?

I know little about cars, I am looking to by one but I am unsure of what to by, I'm looking in the $2500 price range, not concerned about looks. All I can afford is an older car. I also plan on drive from oklahoma to california in september. I know its a silly question. Cheap and dependable. But thought I'd ask. I've been looking on craigslist but I can't compare cars because I know little about them http://tulsa.craigslist.org/search/cto?query=&srchType=T&minAsk=&maxAsk=2500&hasPic=1 thanks for any help