Hi. My wife and I are planning a trip around May 2013, flying from Sydney, Australia to Denver CO. After spending a couple of days in and around Denver, we want to drive from there to Mt. Rushmore and Chief Crazy Horse, etc and afterwards to places like Little Big Horn, Cody, Yellowstone NP, Jackson Hole and anywhere in between that you think we should see. We would be very interested in hearing from folk who have done a similar trip, where we should not go, what we should be wearing (I am aware that this will be in the spring but also that the trip we be mostly in "mountain country". We are not sure whether there will still be snowfall and if we need to hire snow chains? We are anticipating a three or four week trip, at this stage. Would appreciate any advice/assistance in the planning of this trip and I thank you in advance.