We prefer Glacier National Park to Yellowstone. Both are wonderful and you will not have enough time for either!
We have visited Yellowstone 4 time; Glacier 7 times. We spend 12 days in Glacier in 2012 and another 6 last summer.
A problem with Glacier, you never know when the snow will leave. My brother-in-law is has a scout troop pack backing in Glacier last week and most of this week. The entire Hidden Lake trail was snow covered. One of our favorite hikes, the Highline Loop trail, was closed because of snow on both of our last two visits.
Here is a picture taken at Hidden Lake in 2012
A nice morning hike is the Avalanche Lake trail (about 4.5 miles roundtrip)
The Beartooth Highway has been mentioned. Its a great road for a cycle. Heres a view of a segment of the road.
And here is one of the many lakes along the Beartooth.
The Beartooth pictures were taken on June 21, 2012.
Whatever you decide you will have fun and will want to go back for more.
Tom
