D&D have it right. Taxis into town from the airport are about RD$500 pesos or with an English speaking driver US$20 dollars. (Send a note to
palomalinda0890@hotmail.com for a pick up and transfer to Sosúa for US$70 dollars)
The
D&D suggestion is just a bit longer, and it is more interesting since you will be interacting with the "Locals" ..And you can get a cold beer at the bus terminal for about US$1.50....
Since you get in early enough, there will be plenty of time to do this.
HB