I know that at LL they have a hostel and apartments that can be rented by the week or month, but I do not know the details or how to rent them. Try Mark Lasiter at firstname.lastname@example.org
. He lives there during the summer and books custom trips. Check out his website at southamericaski.com. I did not use him, but the people I met there who did liked him.
I agree that the lift system at LL is almost completely dependant on the Marta Lift which operates sporatically, but Portillo has problems too. If the lake is not frozen the skiing on one side is severally limited. The good skiing on the other side is completely dependant on the Roca Jack Lift, which also has a sketchy record of being open, and even when it is the ride up rightfully scares the weak and the timid. Roca Jack es caca loca!