I love how you ask this as though it is an inevitable guaranteed thing to happen :) Fort Knox, or any Fort for that matter. I would personally rather be floating on a boat in the ocean if this were to happen. FAR away from the zombies :)
FINALLY! Someone with a legitimate question on here! Listen, there are many places to go, however the best recommendations I have for you are somewhere remote, where there is a large source of game and water, and is high in altitude, most likely a mountainous region, such as the rockies. Zombies have difficulty climbing, so that is why altitude is important, however the ability to escape should be important too! Make sure you have an excess stock of food and water on hand in case you need a quick escape!
omg... WHY would all of you go to a fort or a store, with all these things blocking your view? the store had isles (idk if thats the right word... [EYE-U'LLS]) i mean lol i would just grab a back pack (full of food) a baseball bat, and a Kevlar vest, and some gloves.... and just go HAM with the bat.... if everyone did this, and people joined groups? ohhh man we would be safe... plus! the bat has unlimited ammo basically, as long as your fit and you can swing a bat to someones face... guns are bad because they have limited ammo, and also the loud sound can lure zombies toward you... see where i'm coming from with this?!?!?