This is more specific information about where Guest Relations is located at each park. It is from post 6 of the disABILITIES FAQs thread, located near the top of this board. You will find a lot of information about GACs in that post.
Where can I find Guest Relations?
Each park has a Guest Relations location inside and outside of the park that will be open during park hours. You do need to go thru the security bag checkpoint to get to the outside of the park Guest Relations, but you don't need to go thru the turnstiles to actually enter the park. Even though they may not sound easy to find, once you are actually in the park area, they are pretty obvious if you are looking for them. They are in the 'wall' of the buildings that make up the outside wall of the park.
At MK, the outside of the park Guest Relations is to the right when you face the front of the park after you go thru the bag check point. The inside of the park Guest Relations is on the left in City Hall after you pass under the train station.
At Epcot, look for the exit from the monorail. It's pretty much straight across from that on the right side of the park entrance. The bag check is closer to the left side of the park entrance, so after you go thru the bag check, go right past the ticket booths and you will find it. The inside the park Guest Relations is to the left, after you pass Spaceship Earth.
At DHS and AK, the outside of the park Guest Relations is to the left as you face the park entrance. This is after going thru the bag check, but before going thru the turnstiles.