Today, I crossed from NJ into Manhattan through GW Bridge, traveled south along St. Nicholas/ Central Park/ East through 59th st/Queensborough bridge, then south through Jackson Ave/ Manhattan Ave/Metropolitan. I'm not pleased with that route. There are too many lights along St. Nicholas. Granted, they are timed so that they open/close together,but there's always a risk factor. Furthermore, ride along Jackson/Manhattan Ave area not particularly pleasant (traffic).
I think the Williamsburg Bridge is better option,albeit perhaps a bit longer in terms of distance.
Question: I know you can ride along the Greenway, but isn't it actually faster to stay on Riverside Drive? The paved asphalt there may be conducive to riding fast and not too many cars? I think at some point Riverside Drive does end (72nd st?). At that point, I could hop on the Greenway and then continue as discussed above?