
Most campgrounds inside Yosemite National Park tend to be booked out up to 6 months in advance! They also seem to be rather crowded, like the rest of the park. You can try to queue for a cancellation (like our Australian friends did), or find a site outside the park (easier at the eastern entrance to the park near Lee Vining). At the time of our visit there was only one "first come-first served" campsite opened, down a rough road (too small for larger RVs), which was full.
Highway 120, the only access into Yosemite from the east, was only opened a few days before our arrival (mid June!) due to rockslides (winter damage)... Highway 140 leading out of the park towards Mariposa/Merced (south-west, our preferred route) was still closed!