(Little late to the discussion)
I live in Colorado and if I had to think where pockets of survivors would be located, I'd say out east of the Rockies where the plains are located which means plenty of farmland or up into the Rockies as well as the high deserts. Towns like Ouray, Durango, Fort Morgan, and maybe Estes Park, might survive due to the smaller populations, while cities like Denver, Boulder, and Colorado Springs would be screwed (and that's probably including the towns located closest to the cities). Hell South Park might actually grow into a town (it's actually three buildings in reality). However surviving here means having to account for our weather system which can swing a lot. In the spring there can be snow or rain, usually lots more snow, until May where it begins to rain...a lot. Summers are typically sunny until where it can switch to an afternoon thunderstorm. The weather here would give trolls and beasts plenty of time looking for more prey, so it would be a matter of people being really vigilant.
Since we're also a landlocked state, we'd have to rely on the transport of goods which would most likely be a really dangerous job.