Went for 10 days to costa rica 2 years ago.
Kayak surfed 5 of them in Mal Pais. Surfers were totally cool with us, and actually had a blast watching us get worked from time to time. They wanted to take our boats out, but after getting them upside down in the pool, they changed their minds.
Did the other 5 days in and around Turialba. Great little town. We used Costa Rica Rios as our guide, but it was pretty disorganized. Still, had a blast. Reventezon is dirty, but probably the funnest section we ran. Way bigger water than anything I have run here in Colorado. Not more technical, but bigger and a bit intimidating at first. All good stuff.
have fun down there!