Tourism numbers are actually up, however, this is only the case in the Punta Cana/Bavaro area. I don't have the numbers to back it up right now, but DR1 TRavel News periodically publishes numbers from the Ministry of Tourism (I believe) and they have confirmed this the last few times I read it, last publication to this effect was a few weeks ago.
Keep in mind that DR Tourism has more tourists from outside the US, then inside, so the credit crunch is more or less limited to the US and won't effect the DR significantly, unless of course the rest of world falls into a 'virtual' recession.