'narrow technical singletrack'...that must suck!
There's plenty of places I'd consider narrow/technical/singletrack that I'd jump at a chance to ride at. 
There are a few guys who live in Edgewater/Ft. Lee who ride over the GWB to Highbridge. From the bridge there are two ways to get there- the way you're asking about up the path on the side of the Westside Highway, or straight across on city streets to Amsterdam then up Amsterdam and into the trails at the 190th Street/Rough Rider trailhead. Here's a google map with both options.
Driving in is unnecessary. The trails are less than 2 miles from the ramp of the GWB, and less than 3 from where you can park on the NJ side and save the toll.
FWIW, I like to ride up there from my apartment in Queens, about 8.5 miles of city streets, as it's usually faster than driving on weekdays. I can make it in 45 minutes when riding, and after work it'll take me an hour or more to get the same distance in the car.
Hey Bob- we were genuinely worried about bike jacking when we were planning the trails. However, in the year and a half that the trails have been open, we've had zero reports of assault, bike jacking or the like. In fact, crime has actually dropped around the park, as riders have displaced the homeless camps that used to define that section of the park, and the 34th precinct has seen less car break-ins around the park as a result. I think most bike thieves in NYC prefer to steal locked-up bikes.
There is a sketchy area around the I-95 bridge that seems to be a crackhead hangout (the cops know about it and patrol it, but there's only so much they can do... there's a methadone clinic across the street and the guys get their morning high there, then hit the park for crack), but the trails are all well north of that. I do sometimes loop down there (last year's race course went through that area), and have never had a problem- I just ride fast and don't stop.
I love riding Highbridge. It's what you'd expect for mountain bike trails in Washington Heights- gritty, tough, sketchy in spots, unforgiving, duurrty. They're not pristine suburban trails, because it's NYC. I ride over glass every day on my commute into Manhattan from Queens, so it doesn't bother me. It is what it is, and we take the long-view with it. In 5-10 years as the neighborhood continues to turn around and clean up, the trails will only get better. 10 year ago police and park staff would barely set foot in the park. We've come a long way and will continue to make progress over the next 10 years...
There is a sketchy area around the I-95 bridge that seems to be a crackhead hangout (the cops know about it and patrol it, but there's only so much they can do... there's a methadone clinic across the street and the guys get their morning high there, then hit the park for crack), but the trails are all well north of that. I do sometimes loop down there (last year's race course went through that area), and have never had a problem- I just ride fast and don't stop.
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There is a sketchy area around the I-95 bridge that seems to be a crackhead hangout (the cops know about it and patrol it, but there's only so much they can do... there's a methadone clinic across the street and the guys get their morning high there, then hit the park for crack), but the trails are all well north of that. I do sometimes loop down there (last year's race course went through that area), and have never had a problem- I just ride fast and don't stop.
