The collectibles are found at the following locations.

At the river side.
At the seaside near Cabrito Park.
At the top of the "tree house".
At the very top of the roller coaster. You can access that location by using the elevator near the entrance of the ride.
In a back alley that has a lot of garbage.
Inside a shop window downtown, near the Walker statue.
Inside the Put-In Hotel (back door).
Inside the Put-In Hotel (front door).
Inside the catapult near the flood barrier.
Inside the sewer near the mutant turtles.
On a grave in the Haunted Graveyard.
On a piece of art in the Art Gallery.
On a table of a balcony.
On the Put-In Hotel Terrace
On the highest roof of the Put-In Hotel.
On the roof of a building near the Put-In Hotel.
On the roof of a building with glass windows.
On the top of a roof top water tower.
On the very top of a wind turbine.