Have you tried this, from Dave Burstein:
"One million New Yorkers can get free WiFi through 187 access points across Harlem, the South Bronx, and Brooklyn in the neighborhoods that need it most. If your WiFi can see smartnetnyc, urbanwifitv or smartnetnych, you should be able to register on the splash page that comes up. When I visited them Saturday, 392 users had logged in by 1:30, although until now they have had zero publicity. more »bit.ly/5hJbaY"