From my experience... Yes, traveling in Colombia is rather easy, often time consuming but what to expect from such a vast country.
Long distance buses - they are rather comfortable, usually with toilets and WiFi. Finding schedule is a problem but you can always ask at the bus station (e.g. at the arrival), We had no problems with reservations or anything like that, being an hour before departure was enough to buy a ticket or two. There was always few seats free (that's in April). I would recommend to equip your self with headphones/earplugs or prepare for Tai martial art movie with Spanish dubbing at max level of sound :)
Local transport... wow, that was an experience, loads and loads of buses, minibuses everywhere and cheap (2-5k cop). They will help you to squeeze in :) and they don't care about time (especially your time). Because there is nothing like bus stop (not many people use them anyway) you and others can jump in and out anywhere you like, safety?... what safety? If you don't know what bus to take, just ask there is always someone to direct you (even if you don't speak Spanish - that's me)
If you travel in a small group, taxi would be often a better option than minibus. Just a bit more expensive (5-15k cop) but you'll be taken straight to place you want. Just agree the price first!