East of Vancouver near Chilliwack, the Foley Lake FSR is a nice area (aka Chipmunk & Thurston) for ATV riding.
To reach the trailhead from Chilliwack, follow Chilliwack Lake Road. After passing the Ford Mountain Correctional Center and then turn left on Chilliwack-Foley Lake FSR. At the first fork in the road, veer right ot the parking area. Start riding back up the road and head back down the other fork (the left one). Ignore the trails in the parking lot since they are kind of short. The main route is long with several side roads to explore.
Note: As of August 2008, the Ministry of Forests Regulations require all ATV drivers to be at least 16 years of age and have a valid drivers license to ride on Forest Service Roads. In addition, the ATV must have valid third-party liability insurance, which is typically around $120 per year. The Conservation Officers will issue a $600 ticket if you do not have proof of insurance.