There are 2 tracks in the town of Marysville, one free the other costs but is watered and groomed with lights for night riding. The free track is called "E street" and is underneath the E-street bridge on highway 70. The other is Riverfront park underneath the 10th street bridge between Marysville and Yuba City.
As mentioned in the other posts, there is Foresthill out side of Auburn, Downiville off highway 20, Stonyford to the west and to the north is a little riding area in Orland.