While waiting in line for a campsite at Zion, we noticed a cyclist was in line several spots ahead of us. I thought that was odd because other campgrounds had spots reserved for people who had walked or cycled in.
After we were settled, we were talking to the camp host about this. He said there are no designated sites for hikers or cyclists. I would hate to have ridden 60 to 100 miles only to find no room at the campground when I arrived so I mentioned that if any cyclist did roll in late, they could stay with us. He said that if we had cyclists camp on our site, the cyclists and us would be evicted from the campground.
So if you are cycling here, plan to arrive early or just pass through.