It's not a bad idea to raid that first military outpost early after getting an AK-74SU and some grenades since there's quite a few supplies, loot from the bodies, and you get the documents from that outpost. But it shouldn't hurt your relationship with Duty (although I'm not sure if you'd still be able to join Duty later if you cheat your way into the Bar like that).
You can push that barrier at the Garbage out of the way in order to access the Bar early, but it will piss off that Duty outpost as they will become hostile to you upon returning.
