You can travel to Spain on modern buses (Eurolines/National Express, for example) from major European cities, including London, Paris, Rome, Frankfurt, and Prague. Although it may once have been the case that international bus travel was significantly cheaper than air travel, budget airlines have changed the equation. For perhaps a little more money and a large saving of travel hours, flying is increasingly the better option.
Within Spain, a number of private companies provides bus service, ranging from knee-crunchingly basic to luxurious. Fares are almost always lower than the corresponding train fares, and service covers more towns, though buses are less frequent on weekends. Smaller towns don't usually have a central bus depot, so ask the tourist office where to wait for the bus. Spain's major national long-haul bus line is ALSA.
Most of Spain's larger companies have buses with comfortable seats and adequate legroom; on longer journeys (two hours or longer), a movie is shown on board, and earphones are provided. Except on smaller, regional lines, all buses have bathrooms on board; most long-haul buses also usually stop at least once every two to three hours for a snack and bathroom break. Smoking is prohibited on board.
ALSA has four luxury classes in addition to its regular seating. Premium, available on limited routes from Madrid, includes a number of services such as à la carte meals and a private waiting room while Supra+ and Supra Economy include roomy leather seats and onboard meals. You also have the option of asientos individuales, individual seats (with no other seat on either side) that line one side of the bus. The last class is Eurobus, with a private waiting room, comfortable seats, and plenty of legroom. The Supra+ and Eurobus usually cost, respectively, up to one-third and one-fourth more than the regular seats.
If you plan to return to your initial destination, you can save by buying a round-trip ticket. Also, some of Spain's smaller, regional bus lines offer multitrip passes, which are worthwhile if you plan to move back and forth between two fixed destinations within the region. Generally, these tickets offer savings of 20% per journey; you can buy them at the station. The general rule for children is that if they occupy a seat, they pay full fare. Check the bus websites for ofertas (special offers).
At bus station ticket counters, most major credit cards (except American Express) are accepted. If you buy your ticket on the bus, it's cash only. Big lines such as ALSA encourage online purchasing. Once your ticket is booked, there's no need to go to the terminal sales desk—it's simply a matter of showing up at the bus with your ticket number and ID. Smaller regional services increasingly provide online purchasing, but will often require that your ticket be picked up at the terminal sales desk.
During peak travel times (Easter, August, and Christmas), it's a good idea to make a reservation at least a week in advance.
ALSA. 902/422242; www.alsa.es.
Eurolines/National Express. www.eurolines.co.uk.
Eurolines Spain. 902/405040; 933/674400; www.eurolines.es.