If I encode an AC3 audio file and author a dvd using the AC3 sound, Will the sound be backward compatible for someone without an AC3 decoder??

e.g.

If I could play it in my Standalone DVD player with full on 5.1 AC3 sound, could I then play it through a PS2 using just the TV for sound or even on a pc through 2chan pc speakers.

cheers

ps. if not, would i have to encode 2 types of sound file into the dvd, an AC3 one and a stereo one?