Well everything I've read has been sadly disparaging about Costa Rican food. We however found some really excellent places there!
In Manuel Antonio, there's a marvelous place called Kapi Kapi. The most amazing dish I've eaten in years is their white marlin. Now we were curious about anyone even serving this since I've never seen it on a menu. The chef came out and said that it is something that sports fishermen catch and when they get back to the dock it is not alive soooo...he makes this fantastic marinated, broiled masterpiece out of it- a perfect dish. The salads were eye-rolling amazing and the key lime pie with macadamia crust was the best! I wish we had more time there to try everything on the menu.
While you are there, if you like salsa dancing check out Bambu Jam. Young, old, local and tourists,all were dancing, no one was sitting!
The Hotel Grano de Oro in San Jose was also one of those great places that shouldn't be missed by any foody. Their 5 cheese plate had some fantastic local cheeses. The salad Silvestri was perfection- blackberries, arugula, gorgonzola, sugared macadamias, strawberry vinaigrette deliciousness - whipped potatoes with ginger sauce- tropical seed encrusted chicken and not to be missed, their 5 chocolate plate for dessert. I could go on and on but if you are in town don't miss it! It's also the nicest hotel in San Jose!