Rancho Naturalista is a birding lodge about 3 hours south of San Jose. Generally people stay at least 2-4 days. The birding, the habitat, and the guide services make it worthwhile for at least that long.
The lodge has its own bird guides, and you will benefit greatly at finding several birds with their help. The lodge is one of the best places in Costa Rica for Snowcap hummingbird, Tawny-chested Flycatcher, and White-crowned Manakin. But it's also good for several species of hummingbirds (you should have at least 15 species before you leave), and a few skulkers like Dull-mantled Antbird, Checker-throated Antwren, Russet Antshrike, and Tawny-throated Leaf-tosser.
Your stay there may include a side trip to the Tuis Valley (offered at the lodge) where Sunbittern, Torrent Tyrannulet, and Fasciated Tiger-Heron are frequently seen. A harder hike up to Silent Mountain can sometimes produce Lovely Cotinga or Rufous-rumped Antwren.
On our trip, we were also treated to roosting Crested Owls, and two Black-crested Coquette hummingbirds.
The food there is good and plentiful, and the accommodations are more than adequate. If you're lucky enough to get one of the two upstairs porch rooms, you're birding experience will be enhanced by quick access to the bird feeding stations.