Forgot about this bug....adding it to list on my workaround thread!
I found the best way to avoid this is to go through the Train Tunnel south of nellis and get to the gate that way. Stay close to the cliffs so that the boomers cant "see" you....and then follow the fence line to the gate. (you would be heading left). Once at the gate....he should come up and initiate the conversation. The only problem with this method is that you have to have 100 Lockpick to get in the train tunnel door south of nellis. (learned from Fallout 3 that having 100 on Science and Lockpick....as well as a High Repair Skill is very beneficial to your "playability" as soon as possible / as early as possible... in the game)
I have tried, quite literally, EVERYTHING....this includes, but is not limited to: taking every possible route to the gate/fence including the train tunnel, attempting to jump over the fence from the rocks (tried with turbo to see if it had any effect and got nowhere), shooting the weapon out of the guard that actually does walk back and forth then holstering my weapon, killing them outright to see if reinforcements would come and talk to me....the list goes on and on and on. And I wonder to myself "Should I even let a game get me this frustrated?", to which I answer myself "Of course, because it's something I enjoy. And no one should be cut short of finishing something that they enjoy. How would Johnny like it if he were to start eating a sno-cone and all of a sudden ninjas swoop down out of nowhere and snatch Johnny's sno-cone out of his poor little child fingers, never to see it again?" This is how I feel, Bethesda! Do something about it!
And yes I have the glitch in the train tunnel with the hole in the stairs to the side room.