What does FULL mean?

The cliche "What part of FULL don't you understand?" comes to mind most weekends.

We put the FULL sign up when we are, duh, FULL. FULL means that we do not have any spaces left to sell to our customers. I wonder, and will ask some people today, what does FULL actually mean to the endless line of people who come to our door after seeing at least 3 FULL signs on their way to our door. Is there some way we can make the message more clear like: HEY, DUDE, WE ARE FULL - GO AWAY. NOW?

There is something else at work here. We are the last hope in our canyon for desperate campers who have promised the screaming little ones in the backseat a weekend of camping. Every campground in the lower part of the canyon is FULL too and these poor folks can't believe that they have been shutout and think that this last FULL sign must be a cruel mirage.

In all fairness, Utahians are the most polite people on earth (and their kids are generally very well-mannered and I have never seen any of them screaming in the backseat) and when these kind souls gently ask if we are full it is not as if some self-important, self-entitled New Yorker was in front of, barking "How dare you to fill up the campground before we got here." Thank God. But it is annoying nevertheless.