The one with the tickets is the second of the two round cans to the right.
You return them to the guy in the internet cafe.
You can look around the island all you want. The "Underground Tunnel Tour" requires tickets. (see related question)
They are in one of the two trash cans near the Tour entrance (under the garbage).
They are in a round trashcan to the right of the Tour entrance. You'll have to sort though the garbage until you find them. (see related question)
Its by the jazz house, or the tunnel. Its in a trash can.
Once you have given a green balloon to the kid in the Countryside (not what you expected), the man at the Internet Cafe will talk to you. Return his tickets and he will give you one to use.
At the end of the tunnel.
You go to the city docks and enter it from there
you have to find the t. in the trash but you have to go to the cafe and get him to look at you
in the tunnel. jump on the light cord to get a paper.
You go next to the tunnel, and the you click on the second trashcan to start looking in it to find two tickets. After you find them, return them to the guy in the coffee shop. He will give you one of them.