LOCATION - enter 5080 N. 40th St Phoenix AZ 85018 into your navi. Park in the back close to the parking structure. Walk down the canal and turn to the right at the first opportunity. You will see a fence (see pics). You can stay there or walk a little further up to get closer to the tunnel. My photos were taken from the gates.
Even though I read all of the reviews, as a visitor to Phoenix who was unfamiliar with the area, I had a hard time finding this place. It was not at all obvious. Since I'm better with an exact address, the closest address is 5080 N. 40th St Phoenix 85018.
I was expecting to see a few bats here and there, but there were thousands of bats flying out of the tunnel and into the night sky. If you stand directly in front of the gate, the bats will fly within inches of you. It was an awesome experience!