According to Jon Murphy, PES Team Leader, the Pro Evolution Soccer 2011 demo should arrive on September 15th for PS3 and PC. 360 hasn't been confirmed.
Quote:
"PESdemo includes four teams, 10 minute games, multiple players or CPU and you can try out all the new team manager options.
For those that haven't heard PS3 and PC demo will be on the 15th. Trying to get the 360 out the same day but unconfirmed right now."