Go Left at the Main Stairs

A look at the public restrooms at Flagler College gives loads of insight into how the Poinciana looked. The "go left..." reference in the title refers to the Men's Room at the Royal Poinciana Hotel.

The Men's Restroom just off the rotunda of Flagler College. The mirrors and fixtures
 are new but the marble walls, sinks and tile floors are original.

Modern urinals with original marble walls, separations and tile floors.

The toilet stalls are intact. The doors might not be the originals but all
 the framing appears to be.  The toilets are modern but the
 overhead water tanks (top left and right) to the originals are still there.

A page from a booklet published just after the Poinciana opened shows the hotel's

 plumbing supplier. Note the overhead water tanks and handy pull chains.

A closer look at the ad: the sink at the right matches the sinks of the Ponce De Leon (top photo.) 

The claw foot bath tub was the standard of the day. The style of the commode is different. 

This is probably pretty close- if not exactly how the bathrooms at the Poinciana looked.

The placement of the bathroom fixtures 
in rooms 251 and 253 at the Poinciana:
The bathtubs are at the top of the room. 
The toilet is right next to the sink. A door
separated the two rooms which could
be converted into a suite.