Several trails to choose from and loop together.
Mt. Tabor is a small but fun park to visit if you don';t want to over extend yourself. There are plenty of hills-easy and challenging--, wide trails, an incredible view of downtown Portland, and the most impressive whoop-dees I've ever had the pleasure of riding. Hazards include lots of dogs, people walking throughout the park, and gravel (especially on the downhill). The trail doesn't get very muddy when it rains which makes this an excellent trial to ride anytime.
How to get there:
Take I-84 to the Northeast 58th Avenue exit. Turn left on Glisan then take your first right (at a stoplight) onto 60th. Continue heading south on 60th past Burnside and Stark Street. About two blocks past Stark take a left onto Southeast Salmon Street and follow the road into the park. You can park near the gate or at the parking lot about ¼ mile into the park on your left.