lots of questions...

You can manage from Leon to Santiago in 12 days, no problem. I am not sure where to go in Leon to get your Credential... find one of the Albergues and ask them, though the Albergues probably have the Credentials there. I think there are 2 albergues in Leon, one in the center and one more towards the outside. You can follow the yellow arrows around town or ask at a tourist center or random people on the streets and someone will direct you to the right place. just ask around for 'un albergue de pelegrinos' and you will find it. people are very helpful towards pilgrims. Leon was one of the only places I got lost in, it is a bit difficult to follow the arrows through, but you will manage.

As for getting there...I am not sure. try flying into Madrid, Santiago, Pamplona, or Burgos if you can't fly into Leon. There is a pretty good bus system in Spain and it isn't too expensive.

Buen Camino!

Well,

You can walk since Leon in 12 days. Another option is to begin in Astorga (10-11 days)

To go to Leon or Astorga there's a lot of trains (http://www.renfe.es) or busses (http://www.alsa.es) Check the one with best timetable for you.

Normally in Spain busses and trains are cheaper than planes.

About the credential, possibly you can obtain it in your first albergue. Or in the Madrid Association, C/ Carretas, 13, 7º, on tuesday or thursday (19:00 - 21:00).

Buen Camino,

Javier Martin
Madrid, Spain