With a taxi for sure...you dont want to do the motoconcho "thing" on that road, trust me

!
Rate is variable...they will tell you that the road is "dangerous"..we negotiated USD$15 and it took a good 25m-30mins due to the numerous bends on that road as well as a fair bit of traffic and poor road conditions once we reached Las Terrenas due to the excessive rains the area had received at that time.
Good luck and enjoy, you are in for a treat...and Hotel Alisei as well as its on-site restaurant are fabulous.
PS Another tip...if you plan to use the same driver for your return trip to Sanchez, take his card/# and he may work out a better deal for you.
If you speak Spanish, I have the number of someone there we know who you could arrange ahead of time so you can PM me if you need it.