Santo Domingo is a no no if you don't have good Domincish/Spanish. You'll find doing even the easiest thing very difficult, no one speaks English unless they are foreign and they are few and far between. Not where you are likely to be living.
EastCoast is boring imo, Central is not Caribeany (and is boring) enough for newbies looking for palm trees and Pina Coladas, and so EastCoast or NorthCoast are the obvious answers. I've never met a newbie that didn't love the NC the first few times, unless you have kids with you. I think moving to a city s great once you've done the initial Caribbean thing. But until you've lived in a beach town you will never settle your mind wondering what you are missing compared to the noisy bullsh1t city.
Try thinking Bavaro/Punta Cana for a seriously laid back life. Or Cabarete for a little more excitement, plenty of expats or foreigners for language not to be an issue, and that little glancing danger you will notice just to spice it up a little.
You need a car where ever you live, so remember that!