I have my PhD in Astrophysics. I won't bore you with any of the details, but I have spent years of studying space as both a career and a hobby.
I'm an avid Grand Theft Auto fan. I've been playing since around 02' or so. When I heard about the "Alien mystery" easter egg from a good friend, I was intrigued. A lot of what I read about the Easter egg corresponded with several concepts I learned while studying for my PhD.
After reading about the Easter egg, I decided to go on a little "Alien" search of my own. I started in that bizarre little patch of rocks with painting on them. To the untrained eye it may just look like a hippy attraction with a few etchings in the stone, but I noticed something that I think nobody else noticed. When looking at one of the rocks, I noticed this sequence of numerals and letters etched into the stone: "6EQUJ5". That sequence is better known as the "Wow! Signal." The Wow. Signal is a powerful narrow wave radio band detected by a fellow from Ohio in the 70's.
Some of the leads scientists responsible for studying this phenomenon say that this strong of a signal could have been created by E.T.s or Extraterrestrials. The only actual scientific explanation that could come up with was some sort of a military frequency, but the military did not take responsibility for it.
As to why this is written in stone, I can't say for sure. There is no way in GTA V to pick up radio frequencies (Other than the Car radio) so I'm not too sure how we could possibly tune into the frequency. The only suggestion I have is that people fool around with the radio stations in their car in this area. I should point out though that in real life, this signal could not be detected by a car radio.
Here is a link for more info on the signal: http://en.wikipedia....iki/Wow!_signal
And here is the picture of the signal etched in the stone: http://tinypic.com/r/vra5o2/8
So with the information I gave you guys, any idea why this might be in the game? Notice anything else that corresponds to this clue? If you guys have any questions about this signal or abut your own theories, feel free to ask!