Bike rides around the North Coast

Personally, I wouldn't ride a bicycle anywhere on the island. Most roads aren't built with any shoulder, and any shoulder that might be there is considered just another way to pass the guy in front. Perhaps more importantly, the majority of drivers don't watch out for bicyclists. They don't care, and if you are in their way, you are simply expendable.

In short, you would be taking your life in your hands to ride a bike here.

there is a Sosua cycling club you might want to contact

The founding members of the Sos?a Cycling Club include:
Henri van de Aa, Peter Bentvelzen, Henk Riep, Cees van Liere, John Leeuwerke, Tanja van der Vleuten, Jos van der Vleuten, Eric Gielis, Gaby Peerens, with Bert Broere (Don Andres) acting as current team leader.
If you'd like to join the club, contact Jos van der Vleuten (tel: 809-931-0226), or enquire at Hotel Don Andres.

http://www.blip.tv/file/2890946/

Biking would be incredibly hazardous on any major road. Iguana Mamas has tours of every level and I would stick with them until you fully understand the risks.