I think you're not supposed to go past the turrets, you're not meant to fight them. there are two ways to do it without fighting them, apparently.
one is to repair the robot. but that requires you to leave the zone.
also, when you leave it, at some point (not sure how it's triggered) after you make it through the Titan Canyon HQ will contact you and ask to go back to Happy Valley and speak to that dude in the Prison. that will open up new dialogue options with him, and you can talk your way inside.
I encountered that Damonta bug, btw, when I couldn't leave it. turns out it's because I had Red with me. had to kill him to leave... oh well, not the first broken quest I encounter