Bluefields has no tours or tour operators. There are several shops and hotels around town that sport prominent Atlantic Airlines signs. These are apparently decoys. Employees in each of these establishments looked at me with utter confusion when I inquired about fares. If you want to buy airline tickets, the best thing is to go directly to the airport, which is only a few kilometers outside of town.
Boat tickets are sold at the pier, and it's impossible to buy them in advance. Most departures leave from an enclosed area on the south side of the main dock. A woman in a small, glass booth will sell you tickets to some destinations. She is the only reliable source of information about schedules and times.