replace all four tires? Help!

I got a flat tire yesterday that can't be repaired as the damage is on the side of the tire. I'm being told that since it's an all wheel drive, it's imperative that all four tires wear exactly the same and if I don't replace all 4, it will negatively affect my drive train and could ruin my transmission.

I've also been told that I can get away with just replacing only two tires because the car is "Real Time" all wheel drive, and the tread will likely wear at different rates anyway.

Does anyone have any experience dealing with this situation?

Thanks,

Donna