Generally they let you through the turnstiles and up the incline to the path between France and England. You wait there until park opens. You are allowed through if you have an early ADR at Akerhaus or a tour, though.
The CMs have to wait for the "Park Clear" signal before opening the turnstiles. That can vary day by day. You are not allowed through the turnstiles until after the CMs have the all clear. AFAIK, the front entrance waits for the same signal. The main entrance guests wait on the walkways between Spaceship Earth and the Fountain until the park opens
In the past, IG guests were allowed up to the area by the Fountain, but that doesn't seem to have happened for quite a long time.