Jut talked to a taxi friend of mine and he told me the going price from the airport in Santo Domingo to Santiago is about 5000DP.
Derfish was correct at about 100 U.S.
I've lived in Santiago the better part of 10 years and not once have I had a bad encounter of any type.
Two years in La Trinitaria, very upscale High Rise apartments with 24/7 security, and a few years in El Ensueno.
Both locations are close to El Monumento. Think of it this way, every city you go to is going to have good and safer areas, and other parts of a city really bad and unsafe.
Nobody can generalize the safeness of Santiago, you will have to inform us, if you know, what area you are going to be visiting. No neighborhood is really safe at night, best not to venture out a lot in the late hours of the evening.