Well, I would head north west preferably. Get up into the mountains, find a place were you have to go above the frost line to get to. Hopefully a vally with a decent cave system ( make certain that any openings that can be accessed from below the perminant frost line are sealetd tight ) were you can obtain food. Pull together any people along the way. While it may be faster and easer to travil alone long term servival of the speaces requires a viable population to provide genetic diversity. It would be better to have such a settlement  set  up already. This particular plan has the benifit of being sound for nuclear and biological attacks. Not just being a decent bet when it comes to a  zombie outbreak as I tend to be of the theory that even walking dead are not likly to move very far when frozen. Though _Ice Zombies_ would make an interesting SciFi original.