Buses and Taxis On the Camino Routes
A lot of pilgrims take buses or taxis along certain stretches of the camino route. They may simply feel tired, they may have injuries that prevent them from walking on a particular day, or they may find themselves behind schedule and need to get along the route a little faster. Some pilgrims do not want to walk along what they may feel are 'boring' parts of the camino (some of the stretches into the major cities are very industrial and noisy, and some people do not like to walk on the meseta). Whatever the reason, buses and taxis are available in most places, and even if you find yourself somewhere where they are not, it is highly likely that someone living locally will be willing to take you to the next village or town. Spanish people along the camino are very friendly and extremely giving. Just ask at your albergue or hostal and someone will help you.
You will find help in getting bus schedules at the albergues or hostels, and locals are always willing to help you call a taxi. In the smaller villages, buses do not always run regularly (if at all). If you are flexible and don't mind waiting around till some form of transport shows up, you will be okay.
On the Camino Frances especially, you will see hand made signage posts from taxi drivers along the way. They leave their numbers so that if you want a cab somewhere along that particular part of the route, you can call them and they'll come and pick you up.
Bus fares are very reasonable, and taxis cost more.
American Pilgrims on the Camino: This site has plenty of information regarding transportation in Spain. They have some great links that you might be interested in exploring, especially if you are travelling to the your chosen start of the camino from France or other parts of Spain. Click on the picture to visit their site.