and you get best rates if you contact them prior to arrival, i have several friends coming over several times per year and they book their car online with Avis Alamo Europcar aso and have the best rates.
there is no office of any car renntal at the PC airport,
the drivers of the car rental companies bring you your car to the arrival area at the Airport and let you sign the papers right there at the little bar.
you can also contact one of those companies once you arrived, their contact numbers are shown at all hotels in the guest service area, so they deliver your car to the hotel.
have fun
Mike