The Dominican Republic has the most international airports in the Caribbean. Since the Dominican Republic is larger than many of the other Caribbean islands an simple mistake in airport selection could place a traveler a four-hour bus trip or US $ 150 taxi ride away from Sosua, when there was an airport less than an hour away.
Since you have a few options on getting to Sosua I will go over them in order from best to worst. Then you can decide which one works best for you time and budget.
First Option – BEST:
Fly in to Gregorio Luperon International Airport (POP) which is only about 10 mins away from Sosua by taxi. It's a small airport in size (maybe 4- 5 gates) but it's served by American Airline, Jet Blue, Delta, Continental which all fly large planes in / out of the airport on a daily basis.
Second Option – BETTER:
Flying into Cibao International Airport (STI) in Santiago is another option (usually not recommended for first time visitors), from there you take a taxi up to Sosua. The taxi ride is about 1.5 – 2 hours, and the cost is about $ 80 USD, but you can usually divide that by up to 10 passengers. You can also catch a bus to Sosua for around $ 10 per person, but you will need to coordinate your flight arrival with the bus schedule.
Third Option – GOOD:
Flying into Las Américas-JFPG International Airport (SDQ) in Santo Domingo is another option (usually not recommended for first time visitors either), from there you take a taxi up to Sosua. A taxi cab from Santo Domingo could cost you about $ 150 but you may save several times this amount in your airfare. Trip from Santo Domingo takes about 3.5 – 4 hours depending on the time of the day.
MONEY SAVINGS: Puerto Plata airport usually the more expensive airport to fly to because it is smaller. I recommend comparing all your options by checking out the cost to fly into or out of Puerto Plata, Santo Domingo or Santiago. The difference in fare can be fundamental at times and other times not worth the hassle.
SCAM ALERT: Beware of taxi drivers that want to charge $ 80 (from Santiago) or $ 150 (from Santo Domingo) per person. Fare is for trip regardless of number of passengers.
SAFETY TIP: If coming at night from Santiago, ask the driver to drive through Puerto Plata, not on the mountain road (too dangerous at night).
Personal Note: I prefer to fly directly into POP and pay the difference in cost (if any) just due to hassle factor of flying into other airports and catching cabs & buses, an especially if your traveling with kids or a lot of luggage.