3speed

Hmm... I think I'm actually gonna have to go with a vintage steel touring bike, but with an internally geared 7sp hub and wider tires with some tread. Like cyclocross tires. Plenty of bag/rack mounts for gear/weapons, but faster than the MTB. Cyclocross type tires should get you most anywhere you're going to go on the bike at speed or for a prolonged period of time. Full on MTB tires are generally only needed for the really off-road type stuff, in which case you can walk it. You're not going to be trying to tackle that if the zombies are actually in pursuit anyway. Then you want speed, not a MTB. And have you ever tried riding a MTB for any distance/length of time? SOO much more difficult and time consuming than road bike geometry and tires with a little less tread.