I'll start with the resort at Bella California first (the pool-side restaurant). The food was fine -- it wasn't spectacular, and it wasn't bad -- and I found that I enjoyed the food but was certainly not blown away by it. Being that I was in Mexico, I was really hoping to enjoy some Mexican food. This was not the case at the resort; it was all American food, I'm guessing to make the customers feel at home. A little disappointing -- the menu should be altered to give guests a choice of national cuisine as well (by the way, the onion soup was pretty good -- we had it a few times).
Now, the resort also has a themed restaurant, "Las Tortugas", and the food here again was satisfactory. Most go for the entertainment, which adds something and keeps you amused, and pasta night was good as were the fajitas, but I think we had the most fun at the "Beach Party", which was definitely entertaining. Although I heard the entertainment staff during the day but did not really take part (except at the beach party), they seemed to do an excellent job of keeping everyone entertained.
"The Office" is a small restaurant located on the beach on the way downtown. It's quite popular, and you'll have no trouble finding it. The food is spectacular, by far the best Mexican food I have ever had. I can't say enough about it. GO -- you won't be disappointed, and being on the beach to have dinner doesn't hurt either. Great food and great entertainment.
While at the marina and mall one day, we also had lunch at Senor Greenberg's. I found the food to be good -- the portions are large, and they also have boxed lunches you can pick up for excursions. They are a very reasonably priced establishment, and we enjoyed their food.