From Montreal downtown take Autoroute 15 North to Exit 67
From West of downtown take Autoroute 13 N to Autoroute 640 E to Autoroute 15 North to exit 67
From East of Montreal take Autoroute 640 W to Autoroute 15 North to exit 67.
The postal code for the lake if you are using GPS is J8B 1N9
Note that some GPS and mapping software will suggest an alternative route via the 117 and the town of Saint-Hippolyte. This is not the fastest route under normal traffic circumstances, but will get you there.
Once you've reached exit 67 on Autoroute 15, immediately turn right at Rue Saint Joseph/Rue Valiquette. In 650m you will reach a "T" intersection, turn left onto Rue Rolland - continue about 11km to the lake. Note that the street name will change from Rue Rolland to Chemin du Lac Pilon at the intersection of Chemin Des Hauteurs ("Les Quatre Chemins" on the map below). Conitnue dead ahead to the lake.