Near San Luis Obispo, the Irish Hills Natural Reserve has 5+ miles of trails open to mountain biking. There are a number of spectacular views of the Los Osos Valley, Morro Rock, Cerro San Luis Obispo, Bishops Peak, and the other rolling hills. The vegetation varies from thick overhead trees to ground brush.
To reach the Irish Hills Natural Reserve trailhead, take Los Osos Vally Road to Perfumo Canyon Road. At 9/10ths of a mile, you will go over a bridge. The parking area is on the left side of road just after the bridge.
Overall, Irish Hills Natural Reserve is the 120th most popular mountain bike trail of all 132 mountain biking rides in California.