I was on the very first docking at Falmouth and it was as you say, largely unfinished, mostly street vendors. It was neat because it was such an event and they made it a big party. Even the little school kids would come running out of thier classrooms to wave at passing trolleys and buses. I'm sure it has gotten to be routine for the locals now and its just another Jamaica port. I'm returning on a Christmas / New Years cruise in 3 months with the whole family and I'm really curious to see what's changed. Doesn't really help you now, but I'll post my thoughts on 'then & now' when I return from docking #2 in January.
Went to Falmouth in May 2011 on Oasis of the Seas. It was like 80% complete, some of the buildings appeared occupied along with various street vendors set-up along the inside of the pier.
As an FYI -- It's a good hour drive to Duns River Falls. A cab ride over will cost you like $60 per person (round trip) then their is a $15 admit fee to get in the falls. It might actually be "cost neutral" to do the tour via the cruise line given the vast distance from the pier to the falls.
Your actually only 20 minutes away from Montego Bay, whoever from the cruise line "claimed" this port was half way between Ocho Rios and Montego Bay is incorrect.
I found the old city tour interesting. Basically we just hopped on the $10 open air trolley ride from the cruise port area that wound through the local roads. It goes through a relatively seedy, poverty stricken area, but there was safety in numbers from the ship. (Would not do a walking tour there). Stopped at a historic church or 2 with adjacent cemetaries. Old English script on the tombstones from the 1700s was interesting. The number of infants buried compared to adults was also eye opening. Only passed one restaurant that I recall and the menu was an old wooden plank nailed by the door with "Chicken, Pork, Beef" or something like that scrawled on it. Definitley not a Chili's. I am sure things are gradually changing as money pours in from the cruise business, but the abject poverty made you feel blessed with your lot in life.