I tried to go up to Alpine Tunnel on the Pitkin side in June 2007 and after Sherod Loop and almost to the Palisades I encountered a snow slide that blocked the narrow road. The road was unmarked that it was closed to all but ATV's. Backing the 1/4 to the first turnout was a little unsettling. Going back I encountered a rock that had fallen on the ROW and driving back around it without a spotter in the passenger's seat, I managed to turn into it. The rental co wanted $2600 for body work.
Marshall Pass was closed by a washout in June 2007 and that can take a long time for the Forest Service to repair. Check the Forest Service website before your trip.
All that said I have driven up to Alpine in October in a snowstorm with no problems. One one trip passed a truck with camper back heading up. Really need a spotter for the right side of the car.
Marshall Pass can be rough on the east side and yet once I found it freshly graded up from the west.
After Alpine go over to Taylor Park by Cumberland Pass and also visit Crested Butte. The old Conoco Gas Station is a museum with a HOn3 railroad diorama of old Crested Butte, most of the old store furnishings are still there.
Bob Meckley