Take the highway from the airport to Santo Domingo.
Take the "?LEVADO" across Santo Domingo. Follow signs (if there are any) to Santiago.
At the huge arch and flag, it may be easier to to to the right. That is Luperon Ave. Take that to the Duarte Highway. Go under the roadway, and up around to the right (I am sure you have driven on cloverleafs before).
Make sure you have RD$30 pesos in $5.00 peso coins or a $50 peso bill for change. There is a toll booth a few kms outside of Santo Domingo.
from there, just follow your nose until the turn off for San Francisco de Macoris. then follow these directions from another set of driving instructions.
4) In Macoris, you go straight into town. You will come to a fork, there are signs, and you bear to the right. Follow that road for about ten or twelve blocks until it comes to a four lane avenue. Then you turn right, and follow that road all the way to Nagua.
5) In Nagua you have to be alert as you come into town since the right turn towards Sanchez and Samana is sometimes not well marked. Again, to the right. (If you miss the turn off, don't worry, just turn right. All roads in Nagua end up on the water and you just turn right again.
From Nagua to S?nchez is an easy run. As you come into S?nchez, there is a fork in the road and a sign indicating Saman? to the left. Bear to the left and you come uphill to the road that leads to Las Terrenas and Saman?. Turn left onto this road and follow your nose. The turnoff to Las Terrenas is well marked if that is your destination. If you are going to Saman? proper, just go straight. The road runs right into Saman?...
Happy trails,
HB 
There is a slightly shorter way:
You can turn right off of the highway and go to Cotu?. You just go north from there, but I am not familiar with the roadds and turns. It hits the highway to Nagua near Castillo I think..
You are probably safer with the first option, this time.
HB
