If you don't want to do the traditional
DDP and only get a few 2 credit signature restaurants out of the deal, the only other way to get to these restaurants would be (and someone correct me if I'm wrong) to purchase one of the other plans Disney offers (I think there is a platinum, silver, etc). These plans include dining but also include other options like shows, water craft, behind the scenes tours, etc. The dining component includes all restaurants and I think there are plans that give you 2 sit down meals a day and others that give you 3 per day. Doesn't matter whether they are "regular" or "signature" when you use these plans. A sit down is a sit down.
But the cost is much, much higher.