I think you could score a nice vintage at that price. I know not a lot pops up on our CL, but with $600 you could even resort to ebay and get a nice score. What size are you looking for I will keep my eye out. As far as riding goes if you want to meet up in Tulsa sometime we can put in some miles. Tulsa Bicycle club has plenty of charity rides also. These are a good way to get into longer distances, they are well supported rides.
-Jake