You can check the whole bus timetable at
http://www.alsa.es
The address of the bus station is:
Av Ingeniero Saenz de Miera,
You will find a useful map of the City of Leon here - you will see a symbol for Estacion Autobuses across the river, close to the bottom right of the map.
http://groups.msn.com/ElCaminoSantiago
Here is an early morning schedule:
SCHEDULES : LEON - ASTORGA
station of origin station of destination departure arrival itinerary from to retail price departure retail price round trip days service transfer seats
LEON ASTORGA 06:00 06:50 show
LEON ASTORGA 07:30 08:20 show
LEON ASTORGA 08:30 09:20 show
LEON ASTORGA 09:00 10:15 show
LEON ASTORGA 09:30 10:20 show
LEON ASTORGA 10:30 11:20 show
LEON ASTORGA 10:30 11:20 show
LEON ASTORGA 12:00 12:50 show
Buen camino!