My very first rides were here at Wilder Ranch, there's no better way to be introduced to a extreme sport than here at Santa Cruz. Best times to come are during the late summer and early fall.
Wilder is located west of University of California Santa Cruz, and can be access from the upper campus for a thrilling 15 miles down hill ride.
It's recommended to park close to Highway 1 and work your way up towards campus through Bay Street and Empire grade, then descend through the park. You should pick up a free map or download one from the web before departing.
The ride can be as short as 1 hour or long as 3-4 hours depending on which loops you are willing to do and explore. For a bit of challenge, try the Enchanted twin loops and be sure to walk your bikes within the ranch (near the exit). Don't forget to check out the horses and other wildlife (hawks, eagles, mountain lions) during the ride.
You do not need to own a mountain bike to enjoy biking at Santa Cruz, there are bike shops (three on Mission Street) that rent bikes for $25/day.
Be sure to grab some food after the ride, mostly American style foods, but avoid the fast food joints and check out "Jack's" near downtown - their home-style burgers are juicy and just done up right.