We stayed at Dona Carmen in December 2008- and found it to be of very poor value. It came in a package, but after a night there, we asked to change to a new hotel/ "posada".
Rooms are basic, but most problematic was the noise (there were parties every night on the main square; since the posada is on the main square, it made it impossible to sleep). In addition, staff was very rude: they would insist for instance to keep the doors wide open the whole night, despite the huge noise. The manager watches soap operas on TV the whole day, and can't be disturbed. Finally, if you arrive 5 minutes late for the dinner (served at fixed hours... from 7pm to 8pm), you will have to skip it... Breakfast food was very poor... some bad ham in a greasy bun... again in stark contrast with the quality found in other hotels.
There are tons of other posadas to choose from (about 60 on Los Roques), that are much nicer, better decorated, better food, and very friendly staff (we went to La Terrassa, but also heard great things on Malibu, Mediteraneo and plenty others)