I can partially answer your question after staying at what is currently the B Resort (two hotels down from the Hilton) a couple years ago. (We stayed during the hotel's transition)
The Hotel Plaza Blvd hotels are split into two groupings, one for each side of the street. Within each grouping there are two bus routes. The first serves Magic Kingdom (via the TTC) and then Animal Kingdom. The second serves Epcot and then Studios. The bus routes you'd be on start their runs there at the Hilton before stopping at the other three hotels (Holiday Inn, B and Doubletree). The schedules will be in the room, and we found the buses to start their scheduled runs pretty close to the published times. (Which are something like "on the :10 and :40 past the hour")
Also make sure to ask what time the pickup times are at the parks, because again they depart at scheduled times. The nice thing about the routing is that if you happen to miss the bus for your route, you can hop the next Hotel Plaza Blvd bus, which should be the route for the *other* side of the street, then just get off at the Wyndham and walk across the street to the Hilton (though I think you have to walk half a block down to the Hotel Plaza/Buena Vista Drive intersection to reach a pedestrian crosswalk).
Edit: Oh, there's also a third bus route that starts mid-afternoon and services all 7 hotels and goes to Downtown Disney, but since you're right across the street it's faster to walk. And with the current DD construction, I have no idea where the Hotel Plaza Blvd bus stop is now...
-Rob
