Why didn't they pick a JUST IN CASE spot?

So, watching it again, at least once every few months as it's my comfort show. Each time, I ask myself why, after they almost lost each other after the farm was taken over by walkers, did they not pick a spot for all the people at the prison to head to if and when the prison went down?

I mean, it would be the first thing I would think of, if I was in that spot, after fearing that I'd lost my loved ones, to have a backup plan.