Ok, here is my take on Costa Rica.  We traveled there in the first few weeks of August, considered HIGH SEASON FOR RAIN.  

First, we made video documentary of our entire experience, so you can follow along with how amazing what we saw was all about :)

We were there for 16 days and covered quite a bit of the country, but there are TONS of places we didn't get to visit, but those that we did get to see...totally awesome.  

We flew Delta one way from Atlanta GA to San Jose.  We stayed one night there before the adventure began.  There is a small airport where we puddle jumped on a 30 or 45 minute flight south to the Osa Peninsula. We stayed here for 4 nights and extended our stay for 2 more  nights, being blown away by a place that National Geographic labels "one of the most biological diverse / intense locations on the planet"

We went on both tours to the Corcovado park....  The video documents ALL of it.   Mind blowing WOW!

Loved staying at the aguila de osa inn!  

Morning meals before the big day of lots of hiking.  late afternoon rainfall dinners.  SO YUM!

Aguila de Osa Tours: (we did both corcovado tours)
http://www.aguiladeosainn.com/tours/corcovado/index.html

We also went to Cano Island: http://www.aguiladeosainn.com/tours/cano_island/index.html
We enjoyed the island for a quick lunch, and feeding the millions of hermit crabs... we snorkeled for a short time, sol got stung by jelly fish...so we got on the boat and did LOTS AND LOTS of whale watching....awesome.  not sure about the seasons for whales, they were mating in August when were there.

We also did the canopy tour at http://www.aguiladeosainn.com/tours/canopy/index.html.  This was ok...the canopy tour is over 2 parts of the forest.  The primary (old jungle) and the secondary (jungle thats been replanted...   This tour was okish....just something fun to do in one afternoon.  

We also kayaked up a little river near the INN... saw alligators, lots of wildlife, and other amazing sites.   The LOUD LOUD howler monkeys will BLOW your mind, just unbelievable.   My video shows all the wildlife we saw just everywhere... mindblowing wowser!

Here is our video from Corcovado:
 

For the 2nd part of our trip, we took the boat up the River Sierpe (serpent) on the way out of corcovado (there are 2 ways in and out, explained in this link)  http://www.aguiladeosainn.com/directions/index.html