As always... used car hunting is right up there with getting a root canal and having your toenails pulled out with pliers.
BUT.. if you must do it... I have to recommend a sales lady by the name of Venus, yes I'm being for real, at Bargain Auto Sales.
Venus is very down to earth and somewhat honest. She seems very willing to help and a definite change from the typical slime ball style of men we're used to in used car sales.
Bargain is a great place for those with credit problems to go to but they are like any of the other 'guaranteed approval' places... depending on your credit rating you will have to come up with heftier down payments.
They do have a pretty good array of cars to chose from and they vary well in price range.
The down side, they play the typical 'car sales' games.. "let me see what the owner says", "how much do you have down because money talks to him", "can you come up with $1,000 more?" and so on. Venus smokes like a chimney and the place ranks of stale smoke.
The plus side, they do have guaranteed approved credit but at a cost of course, extremely bad credit means extremely high down payments. They have a fairly good selection of cars to chose from and all come with an excellent warranty that covers the car fully (again with the reasoning that if you can't drive the car you're a lot less likely to make your payments). And most of all Venus is an excellent person to deal with, down to earth and not a typical used car sales type.