Isabela? the one in Puerto Plata province....past Luperon? On the way to Estero Hondo?
Fastest would be hiring a taxi...no doubt. Cheapest>? Not a clue. It would require a lot of asking around where the parada is.. Maybe taking a Atardecer Mae?a but to Cruce de Guayacanes and then a voladora to to La Isabela...IF that is the one you are talking about...Should not cost a lot, that is for sure...
HB