Regardless of where I am during the initial attack, I have to assume that I at least survive that initial wave. I think there are a few important things to take in to consideration.
-Safest place in the park to wait for help
-Best escape route if it is determined help is not coming
-Weapons
-Supplies
A safe place in the park would mean something that is not easily accessible by the hoard. It should also be easily fortified. There should also be alternate exits. Let's say for the sake of argument that we need to choose a building that the GP can easily get into. I would say no to the Festhaus and Abbeystone due to the outstanding number of entrances to the building.
My choice would have to be Grogan's. Slide some tables and such in front of the doors to barricade them. There's a kitchen around for food. There's also some bar stools that can be dismantled to provide sufficient clubs to deliver the undead back to the earth. I'd try to park it here for as long as I can. If I need to make a run for the exit, I'd try to duck out behind castle o'sullivan. If we're limited to an inpark route, I'd be tempted to just hightail it through scotland and out of the park. But I'm a little skeptical about that route around the highland stables. If you get caught out in the open there, you're undead meat. I think it is reasonable to go the long way around in this case. Once you make it past Lorikeet Glen, I believe there is a first aid station that you can pick up some medical supplies from. You would probably be able to pick up a few weapons from New France and in Octoberfest. There are also plenty of buildings to hide in on the way around the park. Once you make it past the italy/san marco area, I would opt to go to the left and through the Pompeii exhibit. Once exiting to Pompeii, I would take the right fork towards the forest of fun. But don't go in to the forest of fun, that's nothing but a trap. Instead take the path past the skyride to put you beside the globe theater. Now I'm just minutes from the exit. I'd still stick to the buildings though. Once out of the park, I think the safest exit would be through the england parking lot, since there are two easily accessible exits from that lot.
This is very important though, make sure you never make too much noise. This will draw the attention of the zombies and you will soon be overrun. That's why it is important to use blunt instruments to put down the undead as a first course of action.