I would not cancel a trip to Alaska because approximately half of Denali NP is closed. We spent 3 days at Teklanika and took the long 10 hour bus tour from there. It was a grueling trip and didn't se much of interest. Grizzlies, sheep, goats were seen, but were hundreds of yards from us. Teklanika is about 26 miles into the park, so that leaves about 18 more miles to see before the road closure. Really, there's not much more to see beyond that point that can't be found elsewhere in the state. If your goal is to see Denali Mountain, you can actually get better views driving through Denali STATE Park on the way to Talkeetna.
