You could take one of the ferries that run between New Jersey and Manhattan at least during hours when bikes aren't permitted on the PATH. Ferries are more expensive but they tend to be a bit more bike friendly.
http://www.nywaterway.com

Another option would be to get a folder.

From downtown Manhattan, you could take the WillyB to Broadway->Myrtle->Forest Ave, 75th Ave ->84th Street-> 80th Ave.

According to http://www.ridethecity.com/ this route is only 10 miles from the 40th Street Ferry Terminal to 80th Ave. Even less if you were to take the PATH or the Ferry from Christopher Street.