At the last count there were around 1450 people working at the place known as Area 51 in Nevada with half of those being private contractors according to what I've seen. Visitors that are outside the restricted perimeter can be challenged by contracted armed security and advised, actually told to move on back.
I'm watching a team from the 'UFO Hunters' tv series cycle up to the public side of the military base not kicking up any dust attracting attention.
https://www.dailymotion.com/video/x8p0s68