Hi there, Louise!
The Web site www.PortOrleans.org is the most comprehensive fan resource around for all things
Disney's Port Orleans - Riverside (and its sister Resort, French Quarter).
According to the site, "The main (South Depot) bus stop at Port Orleans Riverside is located on the right as you exit from the Sassagoula Steamboat Company main building, just outside the rear exit of Fulton’s General Store.
There are three further bus stops located around the Sassagoula Circle perimeter road:
The first is the West Depot, serving Alligator Bayou Lodges 24-26 and 28-35.
The second stop is the North Depot, serving Alligator Bayou Lodges 36-39 and also Acadian House.
The final stop is the East Depot, which is located behind Magnolia Terrace and also serves the garden-facing rooms of Oak Manor.
Note: generally the early morning buses departing from the South Depot do not then continue on to service the East, North and West Depots, instead heading straight onward to their destination. Other buses will serve the outer three Depots. After 10:30am, all of the resort buses follow the entire route starting at French Quarter, then going around all four Riverside Depots in turn before heading on to their final destination. This can have an impact on overall journey times."
It looks like you might want to favor the building closest to the Sassagoula Steamboat Company, the main lobby. That will minimize your treks to the bus stop, and will also reasonably assure you of being dropped off first. And, based on this information from the fan site, you'll not even have to worry about the other stops on your early morning rides to the Parks!
Have a wonderful time!
See you later, celebrator,
-Deborah B.