You might want to consider the Birthday of Geocaching in Utah Campout. It is held in early Aug on or around the date that the first geocaching was placed in Utah.
Here is a link to a past event to give you a rough idea of the coordinates. It is a fairly nice semi-developed camp area. They get a group area and welcome donations to pay for the site.
I know the link is to the 2006 event, but I believe that they have held it almost every years since the First birthday, and that there are plans of holding it every year in the future.