I love Puerto Plata and I try to give it most of my business, but one thing I would not shop for here, is vehicles.
If you'd buy new, you will want to buy at an "official" dealer which has a history of backing some sort of warranty. Some companies like Toyota (Delta) offer surprisingly generous warranties.
If you buy used, especially as a foreigner... well, maybe in a couple of months, after the world wide economy decline will have had it's domino effect here, you might see a over existence of "luxury" vehicles hitting the market to be turned into cash... but right now... I would not expect to get a competitive deal around coastal locations (when compared to the cities).
Check out Santiago, Santo Domingo first... other's seem to report having found great deals in Moca and even La Vega.
Haggle hard, you have the money, they want it, and it's money which is fast becoming scarce, not cars!
Btw, all older automatic RAV4 and CRV's if tried here, were hopelessly boring gas guzzlers. Before you buy used, INSIST on having it for a couple of DAYS to try (only few dealers will do that, I know, but you may want to rent a similar model at a local rent-a-car to at least get a better feel for a particular car model).
... J-D.