If there are routes, you should be able to find them here, The East Coast Greenway.
http://www.greenway.org/pdf/ny_map.pdf
Unless you go to Queens, and cross over on one of the bridges (not sure they have sidewalks/paths, you'll have to go through part of Harlem.
I used Google Maps, and chose the 'Avoid Highways' and 'Avoid Tolls' options, and it gave me a fairly decent route (or a decent as you can get, riding through one of the most densely populated places in America). With some tweaking, you can probably minimize some of the 'issues'...
I've done a bunch of riding in NYC, and used to live in Stamford, CT, and I can say with some confidence that you will not be able to avoid stoplights, traffic, or bad neighborhoods riding between 59th and 7 and Greenwich. You have Manhattan, Harlem, The Bronx, and New Rochelle to go through. Those 4 places have all of those things plus bad roads. Even the traffic in Greenwich can be crazy.
Good luck
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