The tour garden is just to the left of city hall. As you are entering the Magic Kingdom, you pass underneath the train station. Once you enter main street USA, City Hall is on your left. The tour garden is to the left of that, sandwiched between city hall and a small building that once housed an art gallery. There is a small set of railings and a covered area. If you get completely lost, you can head to city hall and they'll guide you the rest of the way.