Try this
POP to STI, will take an hour and 15 minutes.
15 to 20 minutes to cross Santiago
Not counting the "Oh look, honey, there are some things!!" stops you will make and the obligatory stop to eat at the "Tipico Bonao" where you can call ahead to have breakfast or lunch awaiting your arrival...It will take about 1:45 to get to Santo Domingo and another 30 to 45 minutes to get anywhere in the city, unless your last name is Fittipaldi, and you are driving a Semi sans trailer.
Plan on more rather than less. Report back here just what you did and how long it took. That way we can update our files...
HB:classic: