Spain: What's a good driving itinerary from Lisbon to Malaga?
From Lisbon to Malaga, the first stop should be Faro , 3 hours by car. In Faro you can stay in Best Western Dom Bernardo (50 €) and after a good meal in Restaurante A Taska...
Portugal: Bus or train from Lisbon to Porto?
The best way is by train. Take the alfa train (2H30) in Metro Santa Apolónia
Lisbon: Have 3-4 weeks to unwind on a budget. Should I go to Lisbon or Porto?
You should visit both. First Lisbon and after you can go by the train to Porto (2H30).