In 2020, the 40% of permits designated as walk-up became available for online reservations 14 days in advance. Despite the “W†on recreation.gov, there were no walk-up permits. I think that is still true for 2021. That means that your hypothetical July 12 permit should become available on June 28. Anyone can log in and reserve one. You can send the email to confirm your permit, and you’re on your way, without ever having to make a phone call or go to a permit station.
There are still bugs, especially problems with non-quota trailheads. I went through weeks of emails and phone tag to get a permit for a non-quota trailhead in Humboldt-Toiyabe last year. But recreation.gov is a huge improvement over the patchwork of phone/fax/snail mail hoops that we used to have to jump through. And it’ll get better. In the meantime, you can still dayhike anywhere you like (except for the Whitney Zone) without bothering with a permit.
