I think that the point of going to a high rise though may be that you would possibly have more chance of contact with the outside world - placing some kind of communication up there that there are live people in the building. You really have just as much of a chance running into people of all backgrounds really anywhere (ie Sams Club, grocery store, mall) as you do in a high rise. Thing is, you can just as easily get onto the roof in pretty much any building.
The cool thing about Sams and Costcos here is that they've all got some kind of rafters/pipes/ whatever showing instead of a true ceiling. These would also help to form some kind of boobytrap. They've also got two sets of doors to go through, offering an extra layer of protection for those of us who don't want to get eaten.
