Easiest way: Santiago to Las Terrenas ?

I need some help, please, from anyone who's traveled from Santiago to Las Terrenas:
1. Is it an easy drive and how long does it take?
(I'm used to driving the new highway between SD and LT!)
2. What is the best route?
3. Which bus could I take instead?
Thanks so much for your help!
Susan

Thanks, HB-- You always have the best advice!
I'm emboldened now to get the Budget rental car in Santiago and turn-in at SDQ (unless you have a better rental car recommendation, too!?)
Susan