Man, I am a total zombie movie freak, so I have thought about this so many times. I occasionally work in a big country park, and I'm usually on my own when I work there, so my mind wanders. There's some awesome places to baricade yourself in there, including a massive children's play area along with fairytale houses and a castle. Perfect for survival. There's trees all over, and plenty of spare wood, so with time and effort you could build walkways in the trees. Plus there's electrical outlets in the houses, so for as long as electricity ran, you'd be able to use them. It's a haven.
That's what I'll do, at least.