Spoiler The http://www.uesp.net/wiki/Morrowind:Berel_Sala has the locations of all vanilla NPC's. That link is to the page for the head Ordinator, the one you have to give the letter to.
Red: "Yeah man, shouldn't be too hard to find someone to keep an eye out...for a price I'm sure. Maybe check the Foreign Quarter...in the clubs or the Fighter's Guild."
No, Fliggerty didn't mess up the directions, he just didn't spell it out. Red suggests a couple of places, but doesn't say all the sentries are there or that they couldn't be elsewhere. Although it frustrates me and finding the sentries did make me crazy when I played this mod, I can understand why modmakers don't write walkthroughs. It makes their mods too linear and when the player is done, that's it. Vvardenfell Druglord is not meant to be played straight through, really. It's meant to be played for a while, then you go back to other quests, then you go back to the mod. In the normal course of the game, you would most likely run into everyone in the mod. For instance, the one you're looking for now happens to be relevant to a Thieves' Guild Quest. Fligg's mods are designed to make you think. For instance, where would decent mercenaries hang out? Where would the head of the Ordinators spend his days?