One option is to head to to Pamplona. There are direct trains and buses from Barcelona to Pamplona. From Pamplona you can probably get fairly easily to Roncevalles and presumably over to St Jean.
Also if you are not set on walking from St Jean you can simply start walking from Pamplona - you only miss out on a crazy first day climb over the pyrenees and there are yellow arrows in the centre of Pamplona.
Thank you for the information. Do you know of any web sites for buses around Spain? I was also thinking of renting a car, being from California we love to drive and it would afford me a way to see the country side. has anyone driven this route?
I have the same question! I'll be in Barcelona in June and would like to either start walking from St. Jean or I'd like to make my way to Lourdes (maybe renting a car to check out some surrounding towns) If you can, let me know what you find out!!!
2002 CF: 2004 from Paris: 2006 VF: 2007 CF: 2009 Aragones, Ingles, Finisterre: 2011 X 2 on CF: 2013 'Caracoles': 2014 CF and Ingles 'Caracoles":2015 Logrono-Burgos (Hospitalero San Anton): 2016 La Douay to Aosta/San Gimignano to Rome: