The PIA also has a discount lot with a coupon but, might I suggest a cab or limo? Depending on where you live it might be cheaper and easier in the long run.
I used to travel extensively and it was SO nice to get off the plane, grab a cab, and be on my way home without having to load my bags into a bus, travel to a lot via every other terminal, unload off the bus, reload into the car, drive home, unload out of the car then unpack......