Travel Review: Costa Rica Vacation, Tortuguero, Arenal, Monteverde, Ziplining

That is a great question, and we have already discussed it. I would say one day in the Arenal area is fine, and skip the actual park itself it you are short on time. It's basically just two dirt trails through some woods; you don't actually get up to the volcano. And Monteverde is also a one day thing from our perspective; the zip line activity up in the reservation was amazing, but after doing that you still have plenty of time to see other things in the area. we did not need two days there. And it is very rainy (we were there in March, the "non rainy season") and can be chilly. 

We would want to get to one of the natl parks where you can see volcanic activity better, and also spend more time on the coast/do a sea-faring aspect of the tour. Although Tortuguero is on the Caribbean coast, you cannot actually go in the water because it's too rough. So we got almost no beach or water interaction, which is something we would like to include in our next trip,

Even if you go in the "non rainy" season, be prepared for rain/pack rain gear. it is the rain forest, and you don't want to spend your time running around buying rain stuff nor feeling cold and wet. better to have it and not need it, than to need it and not have it!