2 things:
1) Moving about is much more likely to get you killed. As you cannot control the situation that you are getting yourself into. You have no way on ensuring that you won't run into a horde of a thousand zombies.
While I do live in the city... I do have at least 3 guns in my apt. So I am hoping although my gf admits she wants me to kill her or leave her behind with some sure fire method of death if this were to every happen.. her and I could most likely make it to some wooded area which I would still go to first. Reasons being as I said before.. there are less people.. The zombies even if they retain *some* coordination would most likely be more tripped up by the wooded area's and things like that.. If they aren't tripped up in the woods.. then odds are we are dead anyway.. keep in mind this is all geared towards traveling north to colder climates.
2) Raising rabbits and a small garden is a great way to take care of a family. Rabbit droppings fertilize the garden, the garden feeds the rabbits, and you eat from both. (FYI, rabbits breed quickly. It wouldn't take long to reach a point where you had enough rabbits to have nightly meals of rabbits... it just takes some space, and maintenance.
I'm familier with how fast rabbits breed my girlfriend often tells me about her old rabbit farm she use to live on.
The problem here is maintaining adequate food for the rabbits although a great idea.. if you can not buy feed you must then grow rabbit food.. so you are no longer just growing crops for your family but, the rabbits as well.
The other con is as you mentioned space and maintenance seeing as over time *ALL* places will need some maintaining.. hospitals, stores, jail ect ect.. you would still more or less need an active community to accomplish this.
Don't get me wrong, I do agree with you in a zombie type set up isolation is best and most productive to some degree. Farther away from the population the safer you are.. however, this is where you would really have to work together as a group. A community would be a prerequisite to a large degree. However, the trick is getting your community far enough away from the thread and in a defendable enough position. Realistically whatever zombies wandered up to the colder climates would die quickly.. even if they are reanimated they aren't intelligent enough to safely defend themselves from the environment in a number of locations.. Anywhere that stays cool and has cold winters would be the safest bet.
3) Go to the country and secure a place there to setup. This is good for a couple of reasons. Generally, you can see a ways off and have a warning of any approaching zombies. Also, there aren't that many people in any given mile. I would say that within 1 mile of my house, there are probably 100-300 people. They are also well armed (gotta love country folk). So, what this basically means is.... when people start becoming zombies, country folk will at least kill some of them. Some of them will try to get out of the area. I would have to deal with an initial zombie attack of about 50 to 150 zombies. That's much more manageable than the thousands that would be faced in any metropolitan area. Plus I won't face them all at the same time. So, I'll be able to pick them off as they approach.
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as long as you have more than 150 bullets and your a good shot your safe

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However, there is one thing I think a lot of people also don't consider.. this is disgusting but, talking about the mechanics of the human body.. if your in a hospital/market/whatever highly populated area is around.. you have to deal with not just zombies.. but, the fact that when people die.. they empty their bowels.. zombies themselves are dead decaying organic matter..
This is all highly disgusting.. but, the fact is its more germs than most people *want* to comprehend and a huge source of disease that doesn't even have to be zombie virus related.. we are talking unsanitary to the disgusting power..
While watching Dawn of the Dead I sat back and thought "omg that would be a lot of crap".. could you imagine the smell? I certainly can not nor do I want to.. however, I maintain this point.. urban environment is the most assured way to certain death.
I would idealistically like some sort of "barred in" area with lots of room for farming/community living ect somewhere with heavily wooded area..
However, given sufficient warning I would most likely as said before try to "curb" the zombie invasion...
Given adequate people with adequate skill and resources (which may or may not be realistically achievable.. all depends on the amount of fore warning) We would be able to in any given country side at least create some degree of safe harbor and as someone mentioned before.. guns like AK's have some degree of stopping power.. so even if the military didn't know to shoot for the head.. they do have guns that would saw limbs off or perforate zombies to the point their head may as well be detached.. So while I do not hold my breath.. I would like to think that even if we lost our military as a whole.. there would be enough trained people left with enough skill to A. train others B. create a plan and C. gains some sort of long term control over the situation..
I mean in I think it was night of the living dead.. but, civilians were actually able to patrol local area's killing zombies on sight..
Idealistically even if the threat could not be entirely handled by us as race... given a safe enough situation.. (some degree of space from the infected) its not unrealistic to think that one day "they could all just go away" So long as we managed to stay out of the way of the zombies and hold out long enough (longer than you could store supplies for.. but, "shorter" on the grand scheme of things than most of us would expect..
Realistically the fact that A. people empty their bowels after death and B. most zombies would probably be injured before they got turned anyway.. Their slow moving nature means they would probably accumulate maggots, bugs and other things which would eat them even faster than they would if they were stuck in the ground..
Maggots/bugs eating them means while they will be even nastier.. ultimately.. they are going to lose *more* muscle which means even slower movement.. Lets also not forget that they would not know to stay still or be able to receive help as if they were living.. so attempted movement means further tearing of muscles that are already about to break and will not heal..
We may have a better shot at survival as a race than we thing.. although fwiw I hate "zoombies"