Thanks for the explanations but I am not really sold on either. Both of them (seclusion and the fence) have occurred to me but they just don't make sense. Again, their previous camp was in the forest which had population 0 before the outbreak, and yet zombies found them. It's been a couple of months since the outbreak right? Wouldn't zombies start leaving the cities by this time since there is nothing left to eat there. They attack the animals so wouldn't those secluded areas where animals live be the new zombie magnets. And the fence, yes, there is probably a fence, but then shouldn't there always be some zombies on the other side of the fence, trying to get in. And if you have a a few, they'd make noises and attract others until there's a bunch of them just outside the fence. We never see that in the show. Maybe they go to the fence regularly and quietly kill the zombies that just arrived but we don't see that in the show either. We never see them having trouble driving out because they don't want to let the zombies in when the gate opens.
It's just that the way it's shown in the show, they seem to be too safe on that farm. They walk around casually, windows are sometimes open. They let the kid walk around on his own, even to the forest and that stream. And what about all the shooting when they killed the zombies in the barn? That must have been heard miles away. It just seems like they feel so safe there, as if nothing can happen. I can't imagine being in that house and behaving the way they do.