How difficult is it to get from Sanchez out to Las Terrenas? And how much should it cost?
Not sure you are familiar with the area/terrain?? I would suggest a taxi as we did (would also depend on how much luggage you will have, if any). It is a very windy, mountain road.
I definately would strongly advise against going this route with a motoconcho.
If I recall, we paid somewhere in the UD$15-20 range, well worth it IMO.
Good luck and enjoy.