No, you can play the game without the card but you will not be able to play all of the levels. The three "extreme PhysX" levels, as they are being called by Ageia, make significant use of the Ageia PPU and unless your cool with frame rates in the single digits, you need to get a PhysX card. Look on the bright side though, they are only 150 bucks now.
Honestly, Cell Factor is a great multiplayer game. When the download goes live, I hope as many people grab it as possible because multiplayer on this game is very enjoyable. Single player however is pointless.