Hi,
Great blog. Visited Panama for a couple of weeks in 2006 and really liked the country - the birding was fantastic at all the places I went to. Even without any guide still managed to see well over 400 species.
If you are sailing back north along the Pacific coast, I would recommend stopping at Isla Coiba National Park. Together with Darien, it is regarded as one the last really wild places in Panama/Central America. It is also regularly cited by divers as one of the most outstanding marine National Parks (Whale Sharks, Manta Rays,..). Good birds here include Scarlet Macaws (common!), Brown-backed Dove and Coiba Spinetail, both of which are endemic taxa. On my day visit here, I stopped off at the ANAM Station at the north end of the island (muddy trail) and took a boat to another trail (Aguas Blancas?) about 10 min south. The area around the abandoned prison is also good for birds. The ANAM Station has some relatively basic accomodation and drinking water.