Best way to travel from San Sebastian to Portugal

Barcelona to San Sebastian - either fly Vueling or take the train. By the time you add the extra time needed to fly, the 5.5 hour train ride and the 1-plus hour flight take about the same amount of time door-to-door.

Whether 2-3 days is enough time to spend in San Sebastian depends on what you want to see and do there.

What do you want to see and do in Portugal. I'm planning a trip there, and it seems to me that 1.5 weeks is a lot for just Porto to Lisbon along the coast. What are your interests? When is your trip?

Flying from Spain to Portugal is the best way to go. There is only one night train from Madrid to Lisbon and it’s not a pleasant experience due to the many stops. It is possible to fly from Bilbao or San Sebastián but you will make a stop in Madrid.

There is also a direct night train from San Sebastian to Coimbra and Lisbon, with no need to go to Madrid, but no daytime train on either route.

If you're not finding a flight you like from San Sebastian to Portugal, then try from Bilbao airport.

Backtracking a by relatively short and cheap train ride within Portugal is easier than backtracking across the whole of Spain, or across the international border.