We drive Lisbon Airport - Algarve regularly to our house in the Monchique. With a...ahem...'following wind' and no traffic (there never is) we can do house-LIS in about 2h15 which is not that much longer than house-FAO and of course LIS has better flights and frequencies for us. The A2 is really a great road and if you're going to/from LIS itself, taking the Ponte Vasco de Gama means you don't get caught in traffic in the city.
We have also driven from our house along the A22 (coastal motorway) into Spain and on to Seville, again it's a very good road apart from a rough part across the border where the border posts used to be: it's as if the Portugeuse and Spanish can't decided who is responsible for maintaining the road in this 'no man's land' so no-one does it!