I live in Puerto Plata by choice.
I knew most of the DR before I made that choice.
It's not my first expatriate experience and places I staid include cities in Latin America too, so, I think I know what to look out for.
Yes, as far a work, economy goes, there is not too much going on in Puerto Plata... maybe indeed too little, mostly limited to peddling Real Estate or "tourism".
Certainly, Santo Domingo has way more to offer in that perspective. However, I've found that before I'd live in SD, there are other big cities in Latin America which have more charm, more real culture and a much more diversified economy than SD I would rather choose from.
Without it being in anyway to be interpreted as anything bad, I don't see that Dominicanism mixes well with cosmopolitanism... to me, one or the other goes lost in the process.
But then, that's just me. I could see myself living around La Vega too... in other words, as far as the DR goes, I prefer small cities.
... J-D.