I received a follow-up message from OpenLoveNY's prez regarding the map that apparently is incorrect on Facebook. I very rarely login to FB, so I haven't seen it, but she writes: "The location shown on the map is incorrect - the park is in Queens, basically right across the East River from the where the Manhattan dot is shown. Just didn't want anyone to be confused. Stupid Facebook :/ "
The directions in my previous post should be correct. There is also an informative page about the park, with directions for coming from various places via subway, bus, train, ferry, or car, on about.com: