Taxis seem to be so numerous at times in Bobo...then when you really need one, they're nowhere to be found. These guys are pretty honest from my experience, although some aren't very knowledgeable about certain places.
From Bobo, you might be headed by bus to Banfora, which is a short 1.5 hrs/1000CFA($2), or to Ouagadagou, a 5 hr trip at around 5000CFA($10). Buses vary in size, comfort, and price. In general, sevice and comfort beats the hell out of neighboring Ghana's jacked up transport system. On some of the smaller buses, big bags are tied up on top instead of placed below in the hold.
These guys get you where you're going cheap and fast. Most are very nice, I never had a problem with any of them.