It's open. State run. Only have to pay the $5 per car parking. They groom the track once a week, riders have to water it themselves.
We ended up going to milestone, however, due to my lack of a spark arrestor.
Was a good time. I'm still slow.
That said, I5 is still sketchy.
If you have a State parks pass (alot of people have them around here for beach access) you get in free with that pass.