Photoshop CS 5 & El Capitan
I have been able to determine that Photoshop CS 5.1 does work with Mac OS El Capitan (OS 10.11.2).
On first try, Photoshop did not work, and said a new install of Java was needed, but after that installation was done, it worked like usual. I am experimenting with El Capitan on my laptop before putting it on my primary photo machine.
Here is the link to that Java update if you are not automatically directed there when you try to launch Photoshop: https://support.apple.com/kb/DL1572?locale=en_US