Taking your own vehicle to Morocco is straightforward. There's a variety of car ferries and jetfoils operating between Algericas in Spain and Morocco's Tangier and Ceuta. There are also ferry trips twice a week from Gibraltar to Tangier. If time is your enemy and you've got a bit cash to splash about, consider the occasional internal flight to make the most of this land. The trains are generally comfortable, fast and a better option than the buses - if only because sleeping cars are available for many overnight trips.
Lines go as far south as Marrakesh.
But if you miss the train, the buses are by no means a last-ditch option. The bus network is dense and efficient in most areas. Renting ain't cheap in Morocco, but deals can be struck with the smaller dealers. Take note that Moroccan roads are festooned with police and customs roadblocks. The bigger cities have public bus services and the average ticket price is about Dr2.