Ismenie,
Since your concern is based on what others have written, is it safe to assume you haven't been to DR or if you have are not very familiar with the country?
If that's the case, I'd suggest a taxi from Santiago to Cabarete this time. Roads are pretty good, but this would take some stress off you, let you enjoy the scenery, and pay attention to the route & decide if you want to attempt it next time around.
Earlier this year it cost me in the neighborhood of US$70 for either a van or car from Cabarete to Santiago. About the same it would cost you to rent a car for a day. Hire a driver this time, then you can rent your own car in Cabarete the morning after your arrival & you'll be no worse off financially
Actually, you could rent a day at a time if you won't need a car every day & even save some money. North coast driving is considerably easier & will give you a chance to get used to what pass for rules of the road.
Depending on where you're staying in Cabarete, they will likely be able to arrange for a driver to pick you up. Cheaper most likely & a pre-negotiated price. Probably better than picking a random driver on arrival in Santiago. PM if you like & I can give you the phone/e-mail of a dependable driver... he's the husband of a lady that runs one of the hotels in Cabarete.
By the way, I've driven the route literally 100's of times... the first few were white knuckle affairs.