when are you going? I met a cabbie in Jardines Metropolitana who spoke pretty good english. I never used him but tell me when you are leaving so I can forward you his number and he can pick you up at STI.
Don't know about Racer X's recommendation, but Bachata was referred to me by Hillbilly. I had 2 Korean students who wanted to tour Santiago. Bachata set them up and the girls could not have been happier with the day. The driver called me when he picked them up at the bus station in Santiago, and again, after he dropped them off and saw that they were safely on their bus to return to Cabarete.
You may not need that level of service- and for me, it was unexpected- but, the point is that Bachata has the connections to make sure your driver gives you the kind and level of service you want.