I'm seeing as low as $241 roundtrip on American out in December through March.
Location: Places >> North America >> United States >> New York State >> New York City >> Cheap International Flights from NYC!
Puerto Rico for $289
JFK-SJU on Jet Blue and Delta for various dates . American from JFK is within 10 bucks of this price and United from EWR is within 25.
Obviously not international but still a really great fare to a destination in the Caribbean
This fare is available pretty much through the end of schedule (usually 330 days out) but availability dwindles as dates approach.