Yeah, I reloaded a save before I had entered and told ED-E to wait for me and I still got attacked by the Powder Gangers.I tried to just wipe them all out but there are just so many of them I ran out of ammo for all of my slow firing weapons. I'm only level 4.
Melee, even at low level, works great at the correction facility. I ran out of ammo too, and just melee'd everyone. The trick is to melee first, then on the final building up stairs where there are a lot of enemies, then use your ammo for that part (though I just stealth boy'd and critted everyone for that last part)