It's definitely the west side of EPCOT Center - the trash can and curving lines give that away, those are found nowhere but that section of that park. But the only locations that I can find where there's a walkway, a planter section, another walkway, and then manicured grass (or where there once was manicured grass) are outside of the southern Communicore West building.
My memory seems to recall that it's near the bathroom and that I've sat on that very ledge before at about that same time period, but that's notoriously unreliable (I was 7 then).