My research for travel from Bordeaux to Bilbao has yielded the following results: a six-hour FlixBus ride, or a train to Hendaye, then a bus or a local train to Bilbao. Shall I take a TGV or SNCF train from Bordeaux to Hendaye, then a bus or a Euskotren from Hendaye to Bilbao? Or is it easier to take one FlixBus? I'm more concerned with reliability than ease, but I'd appreciate both. And, on the return, what's the best way to travel from Donostia-San Sebastian to St. Jean de Luz? Thank you for your help!
I would suggest taking the train to Biarritz and then transferring to a bus from there to Bilbao. The whole trip will be a little over 4 hours. Trains crossing from SW France into Spain are always tricky because of the Pyrenees mountains and the topography of coastal, northern Spain.
Thanks, Anita. I'll look into Biarritz.