You could also check out the Puerto Plata Beach Resort apartments a bit nearer the beach (on the Malecon in fact). It has a/c in all rooms, a lounge/dining & kitchen area & a large swimming pool with plenty of garden area around. There is also a security guard on the gate to keep out anyone you want to KEEP out!!
Town centre is a 5 minute motoconcho ride (RD $10) away or a 25 minute walk along the seafront road! If you decide to get taxis, ask the reception to organise you a Tecni-Taxi - fair prices rather than tourist prices!!! Tel. (809) 586 4243. Price - US $18 per night (per room, not per person!!)
Porto Fino is also fairly close smaller rooms & swimming pool but has restaurant/bar on site, there is also ApartHotel Lomar which has decent rooms at US $16 per night!! - Grahame.