Hello Kat.my advice is not to book less than 4stars,then you should not be dissapointed.
The sea can be rough in the north,however,very calm in the south.
Many hotels are in isolated locations so you cannot get out and about.If you like to get about then chose your location carefully.ex. The Luperon hotel in the north is excellent,in about 16acres of ground,but miles from anywhere.
If you like to walk out of the hotel i would recomend Sosua,it's a pleasent town with bars and shops.
Sunscape the Beach is also brill.but isolated
If your hotel is close enough to the capital Santo Domingo in the south its well worth a days visit,plenty of large shops.
Most Riu hotels are excellant,so also are the Bahia Principe hotels
Hope this helps