It depends on the specific camera. Have a look at this list. If your camera is recent, and the list says you need an ACR 7.# version, you are out of luck with CS5, and will need to look at the free DNG conversion download. Good luck
So what can I do if my camera IS on the list, but I still want PS elements to be able to read my RAF files from my Fuji X20?
This is for the benefit of others who might find this thread.
There is a list of the latest Camera Raw versions that can be used with a particular major release of Photoshop or Photoshop Elements here, in the Camera Raw FAQ:
The Camera Raw versions listed in the FAQ (e.g., Camera Raw 6.2 for Elements 8) are the latest that can be installed in a particular editor version.
If that Camera Raw version is lower than the one listed at the link Trevor supplied above, then you'll need to either use the free DNG converter to convert your files to the DNG format before opening them in your image editor, or upgrade your image editor.