Night life for singles is not good in Natura Park. But if you are looking for great night life, you should be prepared to take a taxi and travel to Plaza Bavaro (about 20 minutes, the taxi costs 275 pesos each way). You should try Mang?.. That is the disco from Flamenco Bavaro, free entrance. You can dance there all type of music, but of course also, merengue, bachata and salsa.
Also Areito (in the same area, more or less) in Hodelpa Resort is a nice disco (more tropical, but being a disco, of course..).
Hurac?n Cafe near Melia is a bar on the beach, you can have a beer and dance on the sand.. (great experience).
Near Natura there is a little Bar called "Entre dos Mundos". It's easy to find there many dominicans who work at the resorts.. Good atmosphere..
If you want to know where and when to go..ask people from your resort. They will always give you good advice.
Feel free to ask me if you need more info, ok?