PS - to the OP - I looked around and the normally quoted price for the DDP includes tax - so the 2011 price for the regular DDP is $45.99 non-peak dates, and $47.99 for peak dates - no additional tax will be charged (check the DDP sticky @ the top of the boards).
You are correct that no additional tax is charged on the quoted price.
However, technically, this does NOT include tax (may be important for tax-exempt group).
It is like buying a gift card. When you buy a gift card, you don't pay tax on the gift card. But, when you go to use the gift card, the card is used to pay for the items and the tax. If you paid a tax on the gift card, you would end up paying tax twice for the same items.
The dining plan is the same way: you are not REALLY buying a dining plan, you are paying in advance for the meals (like a gift card).
When you go to pay for the meals with the dining plan, tax is included in the bill and the dining plan pays for the meal, and the tax (though I'm sure the dining plan pays the restaurant a discounted rate than what's on the receipt, and takes out the appropriate amount for the FL sales tax).
I have NO idea how this would work for a tax exempt group, though.