Well Hello There,
I too will be heading to the Westin Riverfront and I am not renting a car. I am going to take CME to the hotel. I'm planning on only skiing beavercreek and vail. The hotel said there is a bus to Vail for $5 each way. I don't know about Breckenridge or Keystone. The hotel has a complimentary shuttle to Beaver Creek and the Village. I really do not think one needs a car here during ski season. To find out about specific shuttle times and locations, you can call the hotel at (970) 790-6000. Have a great trip!