Last week in April
By Oct, 2010, the hotel, casino and conference facilities will be fully open. Casino hotels don't typically open their booking system up that early. When it opens in late April, 1,000 or so rooms will be available. The rest will come on line, over the next 60/90 days.
I suspect that getting a room initially, will be tough, as many of these rooms will be set aside for casino and/or conference guests. Actually, I suspect that getting a room in the MBS's overall, will be a difficult task. MBS will be the best rooms in the city and will certainly have the best view (regardless of which side of the towers you are on). Also, a large portion of the 2,600 rooms will always be blocked off for conferences and for casino guests.
BTW, RW Sentosa got its gaming license today, so I would suspect that MBS will get theirs in time!