If you're looking for adults only, you may have to stick with Punta Cana for the time being. There isn't really an adults only selection in the La Romana. A Secrets on the Bayahibe Beach is planned for construction, so keep your eyes open for that announcement but til then, there's nothing like that.
On a similar thread recently, I posted the following. Maybe something will be of interest to you.
There are soooooo many things to do from La Romana, and many of them are rather one-of-a-kind so it's hard to compare the price or offering to those excursions in other areas. You can book a tour through a tour operator at the hotel to go to Saona Island from a La Romana hotel and pay about the same price as you pay when traveling 90 minutes from Punta Cana to take the tour, or you can take advantage of using one of the local companies which shave about $15 off the price of the larger tour groups. You have that freedom since you are in the area where the tour actually departs and you don't need much for land transportation.
You can also visit Santo Domingo which is only 2 hours away, rather than 3.5-4 hours one way from Punta Cana, or the same from Puerto Plata. You can take a trip to Altos de Chavon, which is another tour that is popular with those staying in Punta Cana, but the drive is 20 minutes from the La Romana resorts instead of 2 hours from Punta Cana. There are the caves just west of the city of La Romana and lots of water tours including diving and snorkeling. I'm among those who believe that the best snorkeling in the island is in the La Romana area. I like the proximity to the residential and commercial village of Bayahibe and the city of La Romana for what they offer. Bayahibe is 10 minutes from the resorts of the area and La Romana is about 25 minutes away. I like to leave the resort quite often and explore the area, which is so easy from these hotels. I have an album of pictures of Bayahibe posted athttp://travel.webshots.com/album/563221847ytecdr
When staying in La Romana, you can fly into Punta Cana, La Romana or Santo Domingo. La Romana is of course preferable, but that gives you lots of options for finding a good deal on the hotel of your choice.
I could go on at length about the benefits of La Romana, but that doesn't have to mean that Punta Cana isn't a worthy destination. It depends on what you're looking for from your trip. I REALLY enjoyed my time in Punta Cana, but since that one trip, I continue to return to La Romana.