We are thinking about driving ourselves from Lisbon to Porto with stops in Coimbra, Nazarre, and possibly other places.
How difficult is it to navigate out of Lisbon? Is there a rental car company on the outskirts of the city? And what rental car companies are recommended? And if we pick up in Lisbon can we drop off in Porto?
I drove into and out of central Lisbon a few years back, and don't remember any dramas.
Centrally, there's a Sixt and a Europcar on the main avenida leading to the major road north and several others including Hertz quite near.
I'm a Hertz fan, myself.
You can almost certainly do a one way rental, but at a cost. You may whish to balance the extra fee with a train fare back to Lisbon, if that's where you are flying from.
It's easy to get back to the airport in Lisbon and rent from there, that way your close to out of town. We did that in September. We used Budget because of corporate account connections. We had no issues. There was an option to return it in Porto but the price would have been almost triple.