Its $15 to ride 1 lap or all day, but remember that its not a commercial deal. All of the bikes are privately owned so if you are a borrower, track time may be fairly limited.
Circleville is way too tight for a streetbike like the YZF, but an absolute blast on a supermoto bike.
http://www.circlevilleraceway.com You are more than welcome to take a few sessions on mine, but you need to provide your own safety gear.
I prefer a dirt helmet, dirt boots and usually wear my leathers. Textile or Leather street stuff will work just fine. Good splid leather gloves are a must.
You might also keep in mind the "you break it, you pay to fix it" rule most guys have on thier bikes. Sumo bikes are really durable and most sport several battle scars already, but at the same time most of us have alot of money tied up in them.
For more info look here:
http://www.supermotojunkie.com/showthread.php?t=82283