The track is open every day, but most weekend days are already booked by either the SCCA or bigger car clubs. Test and Tune is an open day where it's run what you brung. You need a helmet of some sort; any motorcycle helmet will do, open or closed face. Besides wearing your seatbelt no other specialized safety equipment is required. The general idea on the track is no passing in corners and you can run till your wheels fall off.
Normaly it's $60 for 4 hours, but if you get 5 people together, you get one guy free so the price drops to $48 per car. This ONLY works w/multiples of 5 though... 6th guy pays $60
Second Creek is a fun track, not too fast (maybe 90 mph on the front straight) and you would have to do something really wrong to hit anything. A great track to learn on IMHO.