[spoilers]
surprisingly, I skipped the 'hideaway' location and went to the metro directly. while there, I just looked directly at my local map and fallowed my way to that manhole, and on the map it showed an exit, so I just went directly there and saw that the manhole worked exactly like a door.. I didn't have to kill anybody either, I just talked my way through with the 'vampires' and convinced Ian to go back home and the head vampire gave me a reward
[end of spoiler]
by the way, has anybody built the shiskabab yet? It's a pretty awesome weapon I think; a gas-powered flaming sword
sets fire to whomever you strike, real badass