I live in Faro and when I have to fly, I drive to Malaga and fly from there. But yeah, that is not to Porto but international. Never flew inside PT (inside spain, I do fly malaga Madrid with air nostrum ).
when I lived in Granada, to travel to Madrid was either 6-7 hours by slow train, or 1 hr by bus to Malaga then 2.5 hrs by fast train, or... 5 hours by first class bus service directly from Granada. The first class bus included food and what seemed to be unlimited beer and wine for like 30 euro. No comparison. This is my favorite option for point to point travel in Iberia if there is no fast train nearby.