The stop is right behind plaza lama on 27 de febrero and san luis. There are 3 buses a day, but I can't remember the times. I think there is one around 11.30. It is a mini bus with wifi and takes around 4 hours with a stop at a parada half way in San Francisco de Macoris.
I believe it is (Was a few years ago), between 27 de Feb and Las Carreras on San Luis, Esq.with Pedro Francisco Bono, the street before the traffic light at Las Carreras..