Is it really worth staying inside the park? How many days between YSN and tetons would you spend.
Yes it is worth it - It is a big park and if you don't manage to secure accommodations in the park you will waste a lot of time driving into the park before you get to the various attractions. From West Yellowstone, it takes about half an hour to get to the place where you can chose to go north or south. Every day that you visit the park you will have that half hour trip at the beginning and end of the day.
As to how many days - I would spend at least one day in the Tetons. I spent two days staying at the Old Faithful Inn and I did not get to the northeast part of the park at all.
Absolutely. You'll pay more for the privilege, but it's well worth it. And that goes for all U.S. national parks. I'd spend at least 4 full days in Yellowstone and 2-3 in Grand Teton, so you can see everything at a relaxed pace. Yellowstone can get VERY crowded, so you'll want enough time to allow for queues and traffic and not have to skip anything due to time constraints. Lake lodge and Old Faithful Inn are good full-service hotels, and Grant Village Lodging is a bit down in quality but still good value.
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