We took a cab from Biarritz to SJPDP. We arranged it with the cab driver who picked us up at the train station and took us to our hotel. Very stress free. We got to SJPDP before the crowds and went for a light hike in the foothills the day prior to our departure. You will be nervous enough prior to your start, so this eliminates one degree of difficulty. You will miss the train ride to the bus ride, but that's not an official part of the walk anyway. The cost was only a little more for two, than the combination of cab ride to the train station and two train tickets.