I doubt anyone around here has any idea about Chapelco passes, but good luck. You might have to work there or be a resident to get a pass. If there is a pass i can guarantee it's pretty expensive for gringos. At least that's the way it is in Bariloche at Cerro Catedral. I think a pass there is like $1500 US. San Martin is super cool town though. Best ice cream in the world.