See how they ship them. While laying it flat is not an issue the forces that act on the panel while flat could do some damage (potholes, etc.)
If you expect no bumps on the way home, it will be fine.
I am told by the people at best buy that if i were to buy a plasma tv and lay it down flat in my trunk that it would damage the tv. They said that plasma tv's can only stand straight up or else your wasting your money. Is this true?