Hi Jill,
Typically, you can see the performers at
Disney's BoardWalk in action from 6:30 PM - 10:30 PM on Thursday - Saturdays so theoretically, yes, you would most likely be able to see some of the entertainment on offer if you exited Epcot from the International Gateway after watching a 9:00 PM showing of
IllumiNations: Reflections of Earth and walked over to Disney's BoardWalk on a Thursday, Friday or Saturday.
The only way to get back to Disney's Port Orleans Resort afterwards, using Disney's Complimentary Transportation, would be to take a bus from Disney's BoardWalk Inn Resort to a Theme Park or Disney Springs and then from there, transfer to another bus heading back to your Resort hotel.
Alternatively, you could take a taxi from Disney's BoardWalk Inn Resort directly back to your Resort hotel.
Wishing you a magical holiday filled with memories which will last a lifetime!
Emma