No doubt that the Jaragua has one of the best pools and spa on on the malecon. - Since their pool/spa is out of order for a while, i am sure that their bookings are down as well. This means that the other hotels will gladly grab their bookings and up thier prices as well.
As for the Napolitano hotel allowing guests, - Forget about it. Unless you are good at "Sneaking" your guests up to your room then you can forget about it.
Best to find a hotel that will allow guests. - If you are just looking for a good hotel that you can get a good rest at with a great location and no problems with guest (and of course clean and safe), then I would try to the Maison Gautreaux. Send the owners an email and they will take good care of you. The price, location, charm are the best on the island.
Hotel Maison Gautreaux... En Santo Domingo, Algo Distinto.
Tell them David send you...