You can pay cash or card (expect AMEX I believe) on site, you can also make reservations online. If you get there late make sure to use the entrance on Moreno Valley side off Iris and Via del Lago and you can pay in the morning. Make sure to check what sites are reserved before pulling in to an empty one.
I paid cash when I showed up. You pay at the entrance to get in the park. Then you pay at the camp site for the actual camping site.
Yes purchasing for a campsite is possible on site. But there is no gurantee you can get the spot you want closer to the showers or restrooms because it was not reserved. But they do like your money in any form.
Ty Ryan Jeffers
Thanks! Your answer is awaiting moderation.