The Palisades is a reference to the cliffs on the west side of the Hudson River in NJ. I haven't lived in the area in decades and see they have improved the bike routes significantly. Here's a description of the route you were mentioning: Manhattan + GWB to Nyack. Probably not a great choice for a flatlander. I remember a group of cyclists from North Dakota who showed up for a WI race from Madison to Blue Mounds State Park where the last mile into the park was a major hill. Some ended walking. Their practice hill was to use one of the overpasses for the local interstate.

I haven't come across a bike with as limited gear range as the one you list. If you had a 700c rear wheel the range in gear inches is 43.9-87.3 gear inches 27" wheel 43.7-87 gear inches or 26" 43-79.9 gear inches These are rough values as I don't know the exact wheel size and assumes 170 mm cranks. You don't really have any good low gears or high gears either. My recumbent trike has a gear range of 21.9 to 124.2 with a 700C drive wheel. Much better for an area with hills.

You can see the elevation for various parts of Manhattan Island here:Manhattan NYC- Elevation (in meters above sea level) The highest point in Manhattan is just 265 feet above sea level so there can't be any significant hills anywhere on the island.