In general, Costambar is a really nice and quiet place to live (I write in general, I can't promise you won't have a noisy neighbour).
There's a nice beach, some bars and restaurents, no tourism or all-in resorts.
The people who live there, is a mix of europeans, americans and also dominicans.
The streets are quiet too, only people who live there, no motoconchos or guaguas.
On sundays a lot of people also dominicans go to the beach. It depends on you if you take this as positive or negative!
You do need a car, if you'd consider to move there, because for most things you might have to go to POP. (there are only some small markets)
If I had the money to buy a house in costambar, I would not be in doubt.