This last trip had the pleasure of going with True Sportman and fellow CRTer (sorry forgot you handle) to this restaurante.
Exact location eludes me as I wasn't paying close attention but it is very close to the INS building.  Mostly all tico clientele business people.  The place has three sections;  just keep weaving through to the back and it is muy tranquillo.
We each had one of the casados and all were excellent.  I had the dorado a la plancha, very fresh and tasty!  I think the pricing was around 2100 colones.  Well worth it!  (Especially since True Sportsman paid!!!).
Sorry the directions aren't better but worth the exploration 
 
Pax,
Sluthog