3 hours should be plenty of time on a Saturday. Earlier this year I had 60 minutes from deplaning at EZE to scheduled departure at AEP on a Sunday afternoon. I made it a couple minutes before they closed the door. Don't dawdle at EZE, get through immigration and customs as quickly as possible and reserve a remis at one of the booths just past the customs hall. Tell the driver that you're in a hurry but that you want to arrive in one piece
