Bulgaria has so far not really been thought of as a backpacker destination, although it is by all means possible to travel the country on a budget. Locals do it all the time!

There are private bus companies operating regular services between all the major cities and it seems as though the number of people wishing to discover Bulgaria on a budget is increasing as the number of hostels in Sofia and other tourist destinations would indicate. In towns like Bansko or along the Black Sea Coast, rooms can be negotiated with local families for a reasonable rate.
 

Although hitch-hiking is not forbidden and many young Bulgarians do resort to this form of transport, it is not recommended for obvious safety reasons.