Guaguas (vans) are to be avoided, if at all possible, as they are fleet vehicles, driven by young delinquent maniacs.
The public cars (caro publico) charge a few pesos more, but are a lot safer, as they are driven by the owner or one of his family or close friends.
It should cost 30 pesos, (less than 1 US dollar) per person, from Playa Dorada to Cabarete.
You can even negotiate a deal with an empty public car, to take just you and your group, straight to your destination, without picking up other passengers, for approx. 300 pesos, (less than $10 US).