Imbert to Santiago 110 pesos. Caribe Tours to Santo Domingo 280pesos. Santo Domingo to Imbert (on the hour) 330pesos.
I prefer the Espinal bus from Santiago -opp Rotonda. Departs every 20mins. Stops where you want and terminal is by China town.
Metro Train - 40 pesos. Runs every 5 mins. Day passes too.