So I’m going to make one small change to that encounter. While the adventure mentions that the first NPC the players are likely to meet should ‘attack the PCs on sight’, I’ll give the NPC some motive to prefer to deal with them and have them remain alive in the complex...
If this works out, the NPC may point out toward the second set of NPCs in the area and propose some sort of cooperation to advance a common agenda.
Ahhh who am I kidding? The PCs are likely going to be rude to the NPC up to the point where I’ll say something like ‘it grips it’s sword in anger’ and all everyone will reach for their d20s.
This is one of those areas where old school and new school players diverge and not in the stereotypical ways. The new school knows that orcs is for killin'. Veterans of the Caves of Chaos, the D series of adventures, and Danger at Dunwater have a more circumspect relationship with humanoids. I think this is one area where 2e really pushed the envelope, with lots of adventures in Dungeon magazine that had players doing such things as rescuing a green dragon's eggs from magmen. Planescape not only had the PCs playing races that had previously only been monsters but made dealing with demons and cross-dimensional horrors just another day at the office.
There is something the 4e DM can do to shake things up and make the players adopt a more cautious attitude towards encounters, and that is to throw in something clearly beyond their level. Things are so clearly delineated by levels that tossing in a monster that's beyond the PCs' ability to fight straight up is fairly easy to do. Heck, to really throw them for a curve, make it a monster above their tier. If the players know anything about the MM and are paying attention, that should be all it takes to get them to stop and weigh their options a bit more seriously. Once they've had a taste of that sort of play, hopefully they'll look for more opportunities to play like that in the future.
If, instead, they look puzzled and ask, “Is this a combat situation or a skill challenge?”, well, I dunno how to help you there. I really, really doubt, though, that most players are to that point.