While Cuba has decent public bus service, I found it confusing and time-consuming. Tickets can be sold out long in advance, bus station staff can be laughably unhelpful, and if you don’t arrive at the bus station very early (and know what you’re doing), you can lose your seat. While there are very cheap buses for locals, tourists (and locals with more money) opt for the premium service.
Considering the cost, a taxi shared by four can be more efficient and nearly as economical as getting bus tickets. Big, classic American cars can fit a driver plus five. Bucket seats had yet to be conceived of. Trunks are huge.
We had four different guidebooks. While all were helpful, we found even the most up-to-date guidebook to be out of date. Things in Cuba just don’t work in a predictable way. It’s my bet that even if you used the information a month after it was gathered, things would not work out.