Gonzalo and I ate in this restaurant TWICE while we were visiting the Arenal Volcano because it was that good. They serve traditional Costa Rican food, but you can also find foods from other places if you're sick of Costa Rican food.
Gonzalo ordered the squid both nights, and it was very tasty. I ordered the typical plate of Choza de Laurel one night and fish the other night. The meals were served on a plank of wood that was covered with a fresh banana tree leaf. We both ordered fresh juices both times and they were amazing, just like every juice we had in Costa Rica. We had mango, papaya, and pineapple mixed various ways in our four total drinks. We were so full after our dinner each day that we couldn't even order dessert!
Please visit their website to see their full menu. If you're going to La Fortuna or to visit the Arenal Volcano, you must eat here at least once. It's awesome!
http://www.lachozadelaurel.com/ (there's an English option, look for it)