Compared to the States and especially if you haven't traveled much outside the US, Dominican cities may be a little surprising to you, as they reflect a very European layout Eg: people live IN the city or "downtown". Santo Domingo IS a big city, as a matter of fact it is the biggest in "el Caribe" and it offers most of what one would expect of a real city, the nightlife too.
Then there is Santiago which I tend to call "the other" city. It's a typical Latin American city, smaller and less international. The resto of places you'd find on the map are "towns".
However, there's night life all over the island even at daytime, but especially the real Dominican nightlife does not necesairily call for big city infrastructure... it happens every where any anytime... at a gas station, a the corner convenience store, car wash, at beach walk (malecon... every town on the coast has a "malecon"), or in a neighborhood street for what ever reason unbeknowst to most of the attendance, but it is not at all comparable to the nightlife you may be used to "back home" and some, like me, think that's just fine.
On a more humorous note (so, please don't take offence), try to stay away from the sun, girls could take you for a "haitiano" and you might find it difficult to score
Have fun, keep your testosterone and adrenaline at reasonable levels and stay out of trouble. ... J-D.