epcotexplorer:

EPCOT Under Construction: Marking the Occasion

Despite not being a public program, or having a public construction area, until the EPCOT Monorail Line was completed in 1981, the EPCOT Center construction site was marked with signs and art advertising the coming attractions. 

Also of note, the art on the second sign doesn’t reflect the final version of the park, it’s still very much so the 1978 plans.