Here's what I would do...
Get two 120' lengths of Green Line rope:
Green Line - MajorSurplusNSurvival.com Get 6 Caribineers (2 sets):
3 Caribineers - MajorSuplusNSurvival.com Take one of your two lengths of rope and cut it into 6 20' sections for swiss seats. Make sure you sear the cut ends of the rope with a lighter so that they don't fray over time. I always wrapped the ends with electrical tape as an extra precaution. Throw it all in a cheap WalMart backpack.
Learn how to tie swiss seats quickly and practice with the equipment till you're comfortable. This should get up to 6 people out of 11 stories. You could also use one of the caribineers as a quick link if you've got a good anchor point to hook in to. Tie a figure-8 knot in one end of your rappelling rope and put the caribineer through the loop.
That's the safest (yet cheapest) way to be prepared. If you're willing to spend more, here's some upgrades (in rough order of importance):
1) You could drop the extra coil of rope and get climbing harnesses (however many you need).
2) Locking carabineers, but if you're in the dark in a hurry it may not matter - you might not take the time to lock it anyway.
3) You could get figure-8's and have them threaded into the top end of the rope. Then you could just hook into the lowest one on rope and go!
4) You could buy better rope, but as a one-shot escape rope Green Line is more than adequate. I used it as my primary stuff for years and I'm still here to talk about. But there are better ropes (higher breaking strength, smoother, etc.) out there.
OK, how's that for a start? <img src="images/graemlins/smile.gif" alt="" />