South Park: The Stick of Truth - Where to Place the Manbearpig Sensors
South Park: The Stick of Truth is packed with references big and small of the TV show, and Al Gore's request that you seek out the Manbearpig is one of the larger references you'll find in the game.
Finding this side quest is simple: Al Gore is behind a tree next to the Bijou Theater and he wants you, Sir Douchebag, to help him prove the Manbearpig is alive and IN South Park.
Without any spoilers past this part of the quest (or any other quests in the areas you must travel to), here are the three locations where you must place each Mainbearpig Sensor.
Manbearpig Sensor Location 1 - The farm
This sensor must be placed atop the barn at farm. You can get here by climbing the ladders as seen in the image.
Manbearpig Sensor Location 2 - Above Kenny's garage
After completing the main quest objectives in the room behind the garage below, you can break a ladder down in the background debris and climb atop the roof to place the second sensor.
Manbearpig Sensor Location 3 - At the lake
Once you enter the lake area, keep walking left and you will come to this sign. Place the third sensor here.
After all of this, report back to Al Gore at your earliest convenience. There is no rush!