The transport infrastructure in Sardinia is not great. Buses and train connections are not reliable and direct links between places are pretty much non-existent. You can always get from A to B but it will take a long time and you will often have to go the long way round changing in the main towns. If you want to visit Sardinia and enjoy the wonderful scenery to the full, my suggestion is to hire a car.
Road signs are rather limited too, but almost every location is on Google maps so you can easily get directions on your phone.
This is a list of useful numbers to have at hand during your travels in Sardinia:
Medical emergency 118
Fire brigade 115
Motorway assistance 116
Coast guard 1670.900.90