Excellent, flowy MTB trails are 10 minutes away at Palgrave Forest and Wildlife Area. See my log from Saturday. Stay east of Duffy's Lane for the best riding. A couple of the trails are officially for hiking only but nobody seems to know for sure, and there are a few errors on the trail sign so don't worry about it too much.
http://www.palgravetraining.com/uploads/1/2/9/7/12...
The #1 MTB attraction around here is Albion Hills Conservation Area, about 5 minutes further away.
http://www.trca.on.ca/albionhills
Since you don't know the trails, bring a compass and print the map. It's easy to get disoriented. Maybe someone else will be interested in a ride? Normally I'd go but I don't think I can get away.