When we were there this July, no one was there to check in, so you can probably just go to your site early. If not, there is also lot of parking. You can also call as they are there to help you as well with any questions over the phone if not in person.
I will echo Amanda's comment that there is plenty of parking optioñs. Even on the Fourth of July when I was there. Single track bicycle trails traverse up and down the valleys. Very scenic and equally challenging.
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