There are 5 bus stops at SSR:
Grantstand
Carousel (and Paddock)
Paddock
Congress Park
The Springs
So, no matter where you stay, you should be fairly close to a bus stop.
As noted, Grandstand is the first pick-up stop, and the first drop-off stop.
However, if boarding at Grandstand, you do have to ride thru the entire resort before heading out to the park. But getting a seat should never be a problem.