Quoted from Wikipedia

"While the gold-based auction house is available to any player regardless of which region they play in, the real-money auction is restricted to players on their home region. If they use the global play function to play in a different region, they will not be able to access the real-money auction house.[35] Addtionally, the real money auction house will not be available until a short time after launch."

Meaning if we play in US server we can't use the RMAH?