This is a very old post so here is an update from some personal experience. While on vacation back in the US I was injured in an auto vs. bike accident and was wheel chair bound for a couple of months when I returned home here.
We did take a short mini escape to the Blue Bay Hotel in Puerto Plata for a couple of days. It is about 30 min from our home. They were very accommodating and I really had no problem getting around on the chair. Even the beach was accessible. Anywhere there we stair involved the staff helped me up the stairs and carried the chair up as well.
I did find getting around town (Sosua, Caberete and Puerto Plata) was doable but hard at times with uneven sidewalks and curbs. The locals were always around to give us a hand when needed. I did find that when in stores and such there was somewhat of a disregard for “watching out” for me and on some occasions they would walk into the chair as they were not looking down. I also found a complete disregard to handicap parking as any one would park in the space and sometimes that made it difficult.
Overall there was not much that we could not do with me in the chair. One of our favorite restaurants even offered to put a table outside for us to dine as it was on the third floor with no access for me.
I should also note that getting through the airport was a breeze and they took me and the chair through passport, customs and baggage quite easily. In fact I never waited on the line at passport control but rather they took my passport and info up to the desk for me
I would say that vacationing here in a wheel chair is very possible, just let your hotel know.