The national rail carrier in Spain is Renfe, and their performance tends to be a bit inconsistent. Long-distance trains connect most corners of the country for a reasonable price, and usually arrive when they're supposed to. Short-distance and city trains are also affordable but can be subject to delays, especially within the Barcelona area. If you're on a tight backpacking schedule it's worth setting off a little early.
Buses are a great way to travel around Spain on your gap year, as they're affordable, wide-ranging, and usually pretty quick. It can get complicated as each route is run by a different operator, which means at the bus station each operator has its own tickets. If you're not sure, just ask a member of staff.
Feeling flush and in a hurry? Yachts are an amazing way to travel around Spain, enjoy the gorgeous scenery, and distance yourself from the tourist crowds that flock to the coastal destinations.
May is a great time to charter a yacht in Costa Brava, Costa Blanca, or the Balearic Islands, as the weather is good but not too hot and the crowds aren't too severe. In July and August the heat can be offputting on the open water. There's no off-season for the Canary Islands, so you can take a boat there any time of year.
If you want to bareboat in Spain, Americans will need a US Coast Guard License, while everyone else will need a RYA Yacht Master Certification or International Certificate of Competence.
Driving in Spain can be a mixed bag. The road networks are good, but they can also be complicated, with a lot of one-way streets - take a road map. Driving in major cities like Madrid or Barcelona can be stressful, especially as fines for improper parking are uncompromising and steep.
Car is a better option if you're travelling between cities. Roads are simpler and the surrounding scenery is commonly beautiful.
There are two types of highway in Spain you need to know about: autopistas (motorways) and autovias, which are more like expressways. Autopistas are commonly toll roads while autovias are usually free of charge.
It's easy to rent a car in Spain in all the usual ways, and prices are quite affordable as there's a lot of competition between rental agencies. Make sure you get something with air conditioning!
We generally don't recommend hitchhiking in Spain, as the locals aren't too keen on it. You can end up standing at the side of the road for a long time. Your best bet is to talk to people at gas stations or car parks and be as friendly as possible. You're likely to have an easier time of it in the south of Spain.
Make yourself clean and presentable, learn a little bit of Spanish, and your chances of thumbing a ride successfully are much higher.
Spanish cities are great for cycling. Most mid-sized and large cities have extensive cycle lanes. But keep in mind that Spain is a mountainous country, so if you're planning a long journey by bike make sure you're in good shape!