The cruise ends up with bus ride to Madrid. I want to travel throughout Spain. My request is help with best way to get back to US ie RT to and from Lisbon or one way from Spain back to US. I could fly back to Lisbon from somewhere in Spain to make a RT flight. Any thoughts?
Seems Porto would be better to fly into for a Douro cruise. There’s no reason you couldn’t fly into one airport and fly home from another. There’s no need to return to the arrival city unless you intend on spending time there.
Not knowing where you intend on visiting in Spain makes it difficult to recommend an airport to fly home from.
Have you looked at the 'multi-city' ( aka open jaw) ticket options?
You make a single booking of flying into one city and flying home from another. Usually about the same cost as a round trip ticket.
A lot of one way tickets are NOT half the cost of a round trip, so booking one way tickets could cost a lot more.