I believe it is 8AM! Keep in mind take the bus from your resort. Last time we were staying at CSR, and I decided to take our car because I thought it would be better. Well, it turns out they let the buses in early and the cars they hold back into like 7:55-8AM, so we did not arrive until 8:15AM. I was very annoyed and the CM keep saying it didnt matter that they would seat us anyone but I wanted to be ready to be at the park opening at 9AM. I felt if they left people make reservations for 8AM, they should them not make it impossable to arrive for the reservations. After eating if it is before 9AM, then head over to dinosaur ride, and you can be one of the first people to ride it.
We are going to do that breakfast again in Jan, and will be taking the resort bus so we can arrive to our reservation on time!!