We visited at the end of September - probably the best time to visit just before the "Going to the Sun" Road closes. We took the Red Bus tour of the GTTS Road, then drove it the next day. Highly recommend the Red Bus as you get some great commentary from the driver (thanks Matt!). We drove it ourselves the next day to make some more stops, but were unable due to all the traffic on the Road. If you decide to drive the Road, make sure you know what you're getting into. We saw an older couple driving past us, stopped on a hairpin curve, obviously frozen up...felt sorry for them but sympathize also. If you don't get onto the Road, or are willing to hike a lot, you won't get a good look at the Park.