If you have Always Run enabled it will blow your cover. Once your cover it blown no disguise will protect you.

Personally, I just wade through the place killing everything.

If you've previously fought several Dustmen (and/or were unsuccessful in trying to strangle one), the whole place may be tipped off to your presence. For the most part, you'll want to avoid talking to the Dustmen -- except for Dhaal, Ei-Vene, and Soego. It's a lot easier to avoid them if you're disguised as a zombie, but even without a disguise you can simply move away from them if you see one coming toward you (i.e. don't let one of them initiate a dialog with you).

If you've made the whole place hostile and don't want to reload, I think you can just let one of them kill you and when you re-awaken they'll all reset to neutral again. You could also take the direct approach and just fight your way out. You don't have to talk with them to find a way out.

Thanks both of you :)

Uh, seem I am bit late - but as it is another, non proposed option (except by your faq/walkthough): just answer the dusties questions ... not sure what options you get depending on your stats (or if int/charisma is making any difference here) - but looking for an internment or seeing dhaal should be valid answers - no need to be "disguised" as a zombie or to fight on the 3rd floor - with enough dex the "silent" acquisition of a dustie robe (and with that a small memory flash) makes it somewhat "easier" on the 1st floor (no need to talk to dusties, except you want to get out via the main door) - but even there it ain't really needed....

Second this. If a dustman stops you just say you're there to see Dhaal.

And in general avoid dustmen. They should only attack you once they talk to you and you are not able to explain why you are there. So if you haven't yet talked to them simply running around and avoiding talking to them does the trick.