JRFMRF?? I guess you don't know much about the geography of the DR, huh.
Oh well. Your best and fastest trip would be to fly to Santiago from Punta Cana, but I do not believe that there are any scheduled flights. There are flights from Punta Cana to Puerto Plata (About$80.00) and you can get a cab from the airport, about an hour's ride or so.
The boat trip would be kinda hard, since the Yaque river empties into the Atlantic over by Haiti and you are on the Atlantic over by Puerto Rico...Besides the Yaque is not navigable except by flatbottomed boats, and there aren't any with motors. So you see that is kinda out of the picture.
As for the buses, that could be an nice option if you have two days for the trip.,
HB, with a grin....
Of course you could fly into POP, have the family meet you there, visit for a day and then fly on to PC and return from PC to wherever it is you came from...