If you are trying to book the more popular restaurants then yes they could all very well be booked up. Most of the popular restaurants book up at the 180 day window and right now you are about 90 days out.
Maybe try for some of the less popular places. Or call the Disney dining 407-wdw-dine and ask them to check what places are available for your dates. Just give them the date and ask what all is still available.
Use to on the old Disney website you could do that yourself, put in a date and time and see everything that had openings but I am not sure you can still do that with this new sucky website.
I know you can get ADR's at most of the downtown Disney places in less than 90 days. T-Rex, Rainforest, Planet Hollywood, House of Blues, Raglan Road.