We stayed at the Posada Dona Carmen for four nights in January 2006, and found it a so-so experience. The location - right on the beach, and next to Plaza Bolivar can't be faulted, and the rooms were relatively clean. The food however, was pretty grim, and we ended up eating out most nights.
Good for a budgetty stay, but not likely to come back.
I recently stayed in this posada as a part of a package I had. I found it to be in good location and the room I had was by the sea(only 2 rooms have that choice) those are the 2 good points about the place,the room itself was very basic and hot, we had a Fan and the bathroom was old and not hot water although clean. The food was included but it was very simple and nothing to remember, The owner is very arrogant and is always watching TV. I would not recommend this place for a Romantic weekend or if you planned to stay in your room as there are no facilities in there, it's just good enough to sleep and keep your clothes in, in any case you spend the whole day around the beautiful islands