I've been watching my Bocas del Toro, Panama weather for the last several months and the reports are correct. It rains a lot!
This doesn't mean it's un-surfable and the sun never comes out, but it certainly is a burden to one seeking sunny waves.
The months you will least likely experience rainy weather are September/October and February/March.
If you're looking for a live weather feed, even this tiny arcipelago is indexed by Weather.com
Check out this archived image below..... and yes, April 5: lightning and rain!
Sources: Wayfarer, Weather.com