Day 1: Arrival
The drive from La Fortuna to Upala is wildly hilly and has some really stunning views. There are also various farms along the way, including one particular unnamed restaurant/coffee shop atht has a traditional manula sugar cane press. I would tell where it is if I could, but all I can say is look for soke parked cars in front of a house along the highway - the sugar cane juie is worth the stop.
Day 2: Tenorio National Park
Tenorio is another volcanic nationla park, but the real draw here is the Rio Celeste trail. Starting at the park entrance, you follow the edge of the volcano until reaching the famed river and waterfall after roughly 3 km. The river, dyed a sky blue by local minerals, is beautiful in its own right, and you can continue the trail alongside it for another 1.5 km, passing by a large blue pool, before reaching the natral wonder of Tenideros. This location is where the the river's two normal tributaries meet, creating a chemical reaction that gives the river it's famous color.