There is no direct bus service from PUJ to the city. Buses leave from Bavaro Center, they have a stop a mile away from Bavaro Plaza. Make sure you will arrive early to the station, direct bus "BAVARO EXPRESS" operates twice, like at 7 AM and 3 or 4 PM. Ticket is about 200 Pesos. You should take a taxi from the airport to the bus station. If you will miss express you should travel vua Higuey, take a bus Bavaro - Higuey, 1 hour and you will be able to get a direct bus from Higuey to SD, last bus from Higuey leaves like a t 5 or 6 PM.