I use Metro frequently, it leaves from behind the Scotiabank Av. 27 de febrero branch and Plaza Central from Santo Domingo. I?m not sure where Caribe Tours leaves. The stop in in Santiago is also close to av. 27 de febrero, close to McDonalds.
Where do you pay 900-1000 pesos?? The one way cost should be about 190 pesos, (I always buy SDQ-POP which is 340 DOP, and POP-STI is 150 DOP).