Casa Sirena was absolutely lovely and in a great, convenient location in Rincon. We could walk to a few great restaurants, an adorable coffee shop, the beach, and to other activities. The owner was responsive to any questions and the place was clean and modern. We used the neighborhood pool which was enjoyable too.
We did find that the showers were difficult. The water pressure was almost nothing in the farthest bathroom and consistent hot water was hard to come by in both showers (but not in the sinks). I think this may be an issue in Puerto Rico because we also had some issues with the showers in the first place we stayed, so I did not think it fair to downgrade by rating.
I personally do not like firm mattresses, so I did not enjoy the beds, but my husband did! Just a personal preference.
Overall, a great and relaxing experience!