Try Hostal Zapata in Boca Chica. The beach side building is nice and quiet but the room is small. A/C is cold and the shower water is hot!
Hotel Zapata - Boca Chica Dominican Republic
Hotel Mercure is a good choice in Santo Domingo. Pay in advance on the net for the best price.
Hotel Mercure Comercial Santo Domingo: book your Mercure hotel in SANTO DOMINGO