Trust me, from firsthand experience in most any AI resort in Punta Cana you can manage to have a great time if you are traveling alone. Stay at a resort that is centrally located to the nightlife spots like Mangu and you will quickly meet like-minded individuals. Even employees of the hotel (of both sexes) will become a lot more friendly and talkative when they realize you are unattached if you just smile and talk to someone who interests you. (If you want to do anything with a resort employee, you will most likely have to meet somewhere off the resort as they will not risk their jobs by doing anything more than chat with you on the resort property) My first trip to the Dominican Republic many years ago as a young, single, gay, gringo was to Punta Cana, and I was stunned at how bold and forward the employees of the hotel were if you just smiled and chatted with them a little bit. (I spoke to them in English then, as my Spanish wasn't as good then as it is now) Going out to casinos, places like Mangu, Imagine, or any of the local hangouts you will quickly be accosted by locals and once they figure out what interests you then you are bound to have a good time and meet some new friends. My first trip to Punta Cana years ago I would take motoconchos to get around and to my shock the first motoconcho I ever took at night in Punta Cana propositioned me right out of the blue during the ride! I thought it was just a freak thing until it happened again, and again, and again (only while using motoconchos in Punta Cana and only at night). It was then that I realized that the DR is not nearly as anti-gay as people say. Even recently on my last trip to PUJ, I was in a hotel with my other half who is Dominican and there was a male housekeeper who was mopping the floors in the hall outside our room and apparently noticed that two guys were staying together so on another occasion I was returning to the room alone and said buenas tardes and smiled to the housekeeper as I walked by and went to my room. 10 minutes later as I was getting out of the shower to my shock the housekeeper was in the room making up the room knowing that I was in the shower and pretended like he didn't know I was in there! He then hit on my but I turned him down because mi novio es muy guapo, celoso, etc.
It sounds from your post that you have been to Santo Domingo before, so I won't list the many popular venues there. Unfortunately, outside the capital, there is not really any venues exclusively gay. That said, I've managed to have great times throughout the years in La Romana, Juan Dolio, and all over the north coast. (Puerto Plata, Sosua, and especially Cabarete) Staying in Sosua is great because prices for accommodations are generally reasonable and you have easy access via public transport to both Cabarete and Puerto Plata.
The reality is that most Dominicans are totally closeted, and many would never be caught dead in gay venues in the capital. Most meet each other online, and there are many websites that have lots of Dominicans online. If you are staying in other parts of the DR, especially on the north coast, and want to meet better quality guys and not sankies, you would do well to meet them there first.