Where would you go from Atlanta/Hershel's farm?

It's absurd to stay anywhere near Atlanta or any other significantly populated area. Which means: bye, bye eastern America. Gotta go west.

Someplace very sparsely populated,

Where you could grow food (and raise livestock, if you can find some breeding stock that zombies haven't gotten to yet).

Snowy winters -- it'd be easier to spot zombies approaching in the snow. And surely they'd have a hard time shuffling through the snow. Zombies don't seem capable of picking up their legs to get through deep snow, let alone putting on snowshoes.

Can't do California - population 40,000,000 of which 39,990,000 probably are now zombies. And that's not counting the illegal zombies....

I'm thinking Idaho -- away from Boise. Lightly populated to begin with. I'm fond of potatoes. There are probably a number of super-rich survivalists around Sun Valley who retreated there early in the zombie crisis. They're lonely now and would welcome some company, I think.