We just got back from a 6 day trip to Culebra. We hadn't found much discussion here prior to our trip, so I thought I would offer up a trip report. As noted in many previous discussions, the options here are limited and nothing like Puerto Rico, but we actually were pretty happy with most of our meals.
Dingy Dock: We went here on our first night. With its location on the water and a more touristy look, I was prepared to be very disappointed. Actually, our meal here was very good. We shared the empanada of the day, which was delicious, and the fish entree that I got was very well cooked and seasoned. The atmosphere, view, and feeding the tarpon made this a memorable dinner. Not the best meal ever, but a pleasant surprise and good start to our trip.
Zaco's tacos: This was probably our favorite spot. We particularly enjoyed the fish tacos. Again, not the best I've had anywhere, but tasty, fresh, and reasonably priced.
El Caobo: We tried to go to Barbara Rosa's only to find it closed that evening (Wednesday), but she sent us to the nearby El Caobo, which she described as a local favorite and where she goes to eat. This had a very local feel, a somewhat gruff owner (who did eventually seem to warm up), and very good, simple, local style food. I had a chicken in garlic that was delicious.
Barbara Rosa's: We went to Barbara Rosa's the next night. Food was simply prepared, but fresh and we were happy with our dinners. Note that this is her cooking in her kitchen, so it's worth getting there early because there will be a wait on the food. It's BYOB, which makes the reasonable prices even lower. Mosquitos weren't terrible when we were there, but it's worth taking bug spray.
El Eden: This was the biggest disappointment of the entire trip. Several people had recommended it, and we were not impressed. The atmosphere was like a college bar, the tables were VERY close together, and the menu had a very dated 1980s feel to me. I got the lobster risotto, which is their signature dish, which was underwhelming. Expensive and not worth it.
One day we went on a sailing catamaran trip with Captain Bill (Pela Vez). He provided snacks, and a late lunch/early dinner which was very tasty, particularly given the small space he was cooking in. Yummy fresh fish. This was a really fun day, and I would recommend it. The good fish was just an added bonus.
Susie's: This restaurant had the most innovative menu that we saw. It was a little inconsistent. Some of the dishes were outstanding, some were just OK. Great atmosphere and friendly service, so definitely worth a try.
We ate several lunches at the Kiosks on Flemenco Beach. We particularly liked the mufongo at Kiosk #5 (though it takes awhile). They also had good chicken kebobs.
So all and all a good trip. This is definitely not a foodie destination, but the beaches and snorkeling were amazing. If you go with the right expectations about the restaurants, there are some good options.
Incidentally, the grocery stores were TINY and very unpredictable in what they had. There was a good selection of Puerto Rican rum available for reasonable prices.