This hotel/motel is right on the main street in downtown Santiago de Los Caballeros. It is not expensive: $37 USD per night and it comes with air conditioning and fast wifi. It is on Calle Del Sol in the city center. I live in Santiago full-time and have walked by it many times.
The address is:
Calle del Sol 50, Santiago De Los Caballeros 51000
Here is the Google maps: