when are you talking about?
i'll have a vehicle and will be going from samana back to sosua probably the 19 or 20th of january. could easily give you a lift.
regarding the chicken bus:
i've also done that many times and found it to be a rather fun experience. one trip, the driver had 3 large presidentes (that he split with a lady in the front seat) by the time we got to puerto plata. another, the bus broke down between boba and cabrera. after some passengers transfered to a passing taxi, it mysteriously started again and we had no further problems.
i got pics of that one:
http://www.latinamericanlady.com/page3/images/P1000194_JPG.jpg
http://www.latinamericanlady.com/page3/images/P1000190_JPG.jpg
the seats aren't as good as caribe or metro, but they're not near as bad as a guagua.
get there early and grab the window seat by the door.