It is not the French Ministry. The ride takes place in the British Ministry, which was confirmed by the official details revealed a few weeks back.
The ride entrance will likely be themed like a Metro station, but a Wizarding one, so a Floo Metro station, sort of like a Subway station but for Floo travel.
PS. The square where the entrance to the French Ministry is located (within the film it appears in,) is actually built, and can be found on the far right side of the land... there just is not a way to enter it.. (yet). Maybe someday that can be the setting for a new attraction.