If I turn off iCloud will it delete my photos

If you turn off iCloud Photo stream on the device, Photo stream, and the images in the stream folder, are removed from the device, BUT NOT FROM iCloud. If you have any other devices using iCloud photo stream, they will not be impacted. You can also delete from photo stream, just like any folder.

If you have a Mac, I strongly suggest that you use iPhoto, and link iCloud to it. This will allow iPhoto to automatically download all photo stream images, and safely store them on your hard drive. Then no matter what, they will be saved.

If you only have the one device or you sign out of iCloud for images, then Apple holds your images in the cloud for 30 days, so you can simply reconnect and the images will still be there. See this article: http://support.apple.com/en-us/HT201317

Turning off icloud photo's will not delete the photo's in your camara roll because the photos located in that folder are taken by your device.

When turning off icloud photo's, you will get a message that you are going to delete the icloud photo's on your device. The photo's will still remain in 'the cloud'.

When you turn off icloud photo's (complete) you have 30 days to download the photo's on iOS, Mac, Windows, or via icloud.com, but this feature is still in beta.