John,
Welcome to DR1. It would be my suggestion to take a bus rather then a taxi unless the price is not important to you. Also, with the hour you are arriving it would probably put the bus trip out of the question and therefore require a taxi if your Sosua arrival time must be made on the same day. The reason I say this is because of the travel time involved, regardless of which mode of transportation, but the added problem of insuring a bus from Santo Domingo to Sosua at the hour you would arrive there.
I have inclosed some links for you to read.
Found this for your reading pleasure;
Taxi's vs. Buses
Coming to Sosua from Punta Cana or Santo-Domingo
Best way to get to Sosua from another airport
Bus:Punta to Puerto
Other board members should be with you shortly to offer their help in this matter.
Rick