You definitely can't turn it around before the minimum weight. And the longer you wait the better. Rear facing is much safer and it's recommended that you keep it that way as long as possible, and at least until age 1. Our DS2 was nearly 2 before we turned him around - but he was small for his age.

I'll try and find the youtube clip on the safety aspect - once you see it you won't be in a hurry to turn the seat around.