The term has its roots in the resort, park service and service industries and can easily be dated back at least as far as the mid 1970's. It is widely used throughout the US, but may not be in general use by mainstream society.
Mostly an inside "Joke", created to vent emotion when dealing with the public.
In Yosemite National Park, "Tourons" regularly block access into the park by stopping on the single lane road to take pictures of wildlife.
"Tourist, Please leave your brain before entering " was the sign in an underground cartoon in Yosemite in the late 1980s. It depicted the entrance to the park with a park service employee leaning out the gate to accept the brain of a tourist driving a Volkswagen Beetle. Another sign in the cartoon read "Night Drop".
The cartoon was seen in both park service and concessions offices during that period and reflects the over all harmless, yet critical view of people who forget how to act in public.
Used by tourist trade to describe bumbling visitors; compound of "tourist" and "moron".
Adj: The Tourons are here and traffic is backed up for miles.
"Why did he stop in the middle of the road?" "He is a Touron and too old to read the street signs."
"Damn, now that it is cooler all the Tourons will be here soon."