Inside the upper bungalow, near the bridge of Paradise Survival Camp
In the second floor of the Halai Village survivor camp, near the doorway.
Inside Jimmy's workshop in Marik's Marina by the workbench. You can get inside the workshop by jumping over the broken wooden ledge northeast of the workshop.
In the second floor of the Santa Maria mission building.
On the table inside Dr. Kessler's lab.
During Chapter 6 in the main quest “The Tunnels”, you'll eventually reach the massive hall with the radar antenna. Take the stairs to the left and check the shelf inside the collapsed storage room to find this diary.
Inside the makeshift hospital, on the counter near the door.
On a table of an outdoor cafe, outside the infected warehouse south of the cinema.
Inside a tray west of Frankie O Hara's apartment.
Inside a small barricaded area southwest of George Serero's apartment. This is just beside where you can Rescue the NPC Gianna.