Never done it but seen lots of people mountain biking up and down Marys Peak. If you have never been to Marys Peak its great on a clear day you can see the ocean when you look to the west and mt. Hood to the east along with Corvallis and the rest of the valley. Their are a lot of cyclists around here so much so that when the weather is nice you have to drive slower do to cyclists. I have seen groups of 10-15 or more cyclists.