Instructions
Check the DVD set-up menu. There should be an option listed for subtitles, whether it's closed captioned English or foreign language. Be sure this is set to off.
Play the DVD. If subtitles are still appearing, push the triangle button on the PlayStation 3 controller to bring up the PlayStation 3 playback settings menu.
Push X on the subtitles icon until you see "Subtitles: Off" in the bottom left corner of your screen. The subtitles should immediately be gone.