buy a knee brace (donjoy armor is a good one) and ski until you can have surgery. I played hockey and lacrosse and skied with that brace until I had my surgeries done. As long as it's just the ACL that's torn, there shouldn't be any pain, just instability.
http://www.kneeshop.com/proddetail.asp?prod=11%2D144X%2DX
that's what most doctors will give you (not necessarily that brand or model, but that kind of brace).