Maybe you've got your answer by now, but there is a good and always improving homebrew shop in the Pavas area of San José (west of Sabana and easy to get to). TicoBirra. Also on the east side of town is the Bodega de Chema. Both have done a great job of teaching new homebrewers and really growing the culture here. Their selection of ingredients and equipment is growing all the time (though for lots of logistical reasons, not as good as US shops, but that's the goal and they're always trying).