According to Kensington Blog, wi fi hotspots include the Picnic House and the Boathouse. They’re out there and I haven’t tried it yet.

The New York City Department of Parks & Recreation, in association with WiFi Salon and Nokia,
is providing free WiFi access in selected parks. There are currently 17
designated wireless internet hotspots throughout the city available to
laptops, PDAs, and other internet-ready devices for those who have no
internet access or, simply, individuals who enjoy some fun in the sun.