The use of PVC conduit exposed inside a building is generally a violation of the building code. The "Smoke Contributed" rating of PVC is far too high for this kind of use. Metallic conduit or Electro Metallic Tubing using factory made bends is nearly as easy to work with and provides better protection to the conductors. I would think that the simplest way to do what the OP wants to do is to install an extension ring over the existing switch box and use a knock out in the extension ring to begin a run of EMT to a surface mount switch box on the other side of the garage. If the ceiling is smooth it will only take two box offsets and two ninety degree bends to route the EMT which should make for a fairly easy wire pull.
-- Tom Horne