JMO but I'm pretty sure BB have been offered to resort guests in May. If you've read BB's are never offered in May, the posters might mean that there are
usually no May dates on the flyer to choose from (at least there haven't been last few years) or that the
Free Dining BB is never offered in May.
Of course you never know what they will offer this year, but if you are a resort guest in May, you might be offered a BB similar to the one currently shown on Mousesavers:
20% off rack rates at Value resorts; 30% off rack rates at Moderate and Deluxe resorts; or 40% off rack rates at DVC/Deluxe Villa resorts.
The dates recently being offered to book a return trip are
5/31/09-6/6/09, and 8/23/09-10/2/09.
Let's just speculate that this is the BB you get. If you are there in May, you might not want to return between the 8/23-10/2/09 BB dates to choose from on the flyer. In that case, I have read posts of DISers booking a BB with whatever dates were on the flyer, then switching when they read about a new BB offer that opens with dates they did want. You might want to post for advice from DISers who have done that to see if that works.
Of course by May, there might be a different BB, with different dates, but it will probably
not be the Free Dining BB (which is probably the one that you've seen before in September) that is usually offered to Free Dining guests. I'm guesstimating that one will start in August when the Free Dining period starts.
Good luck! When you get there check your room and TV channel or be sure and call ext. 8844 from your resort room to make sure if/what BB is being offered to you
