An adventurous undergrad once emailed me for advice about teaching English in Spain. At the time, I didn't know much about the topic, as I'm in Andalusia to do fieldwork and not to earn money, per se. Since then, however, I've made many friends here who do teach English, and have learned quite a bit about the topic, which I'll pass on to those 'traveling educators' interested. 

The Junta de Andalucía offers a special program that hires U.S. and Canadians citizens to teach English at public schools in Andalucía for one year. Keep in mind that public schools in Andalucía are probably very different from wherever you may be from. You can expect to spend just as much time asking your students to be quiet as you will teaching; Spaniards love to talk, and most are not about to stop simply because they're in a classroom. Most students, at least in Andalucía's public schools, have little interest in learning a foreign language, as they will probably never need one, and the region's public school system is notorious for failing to instill in its student body a culture of learning. In all honesty, I've never heard a foreigner who has taught (or been a student) in the public school system here have much to say that's positive about the experience. However, if approached with the right attitude by someone adequately prepared for what is to come, I imagine there would be much gain a lot from the experience. 

Here's the link to the Junta's program, which hires English teachers for the entire autonomous community of Andalucía: http://www.ciee.org/

Your best bet lies in landing a position at a language academy. Students in these settings are sometimes more driven to learn a second language and can include adults who need to learn English in order to perform well in a profession. Qualifications are important: Almost no one will hire you simply because you are a native English speaker. Most applicants won't be considered without CELTA certification, and experience is preferred.

Incidently, for either of these types of employment, if you're considering coming as a tourist and just overstaying, meaning you'll be in country illegally -- forget it. You won't be hired. The good news is that, if you are qualified and are legally residing in Spain, jobs for English teachers are plentiful and easy to find.

Of course, once you've been in country for a while, you can always offer private classes. There are numerous pitfalls and benefits associated with this, but these won't matter to someone just entering the country, as it's only a viable route for those who have already been established.

Keep in mind that Spain is a developed country, and that the cost of living is higher than in many parts of the U.S. And, unlike the U.S., where the cost of living decreases as salaries decrease, the cost of living in Andalusia is high even though wages may be miserable. The average rent for a flat in Seville is around 600€ a month; unfortunately, that's also about the average monthly wage for English instructors. I'm not kidding when I say that some farm hands working in the olive groves earn more per month than do many English instructors. See this as an opportunity to bond with a good friend, if you have one adventurous enough to travel with you and split the rent after arrival.

This link from SleepNgo http://www.sleepngo.com/ is a good place to start either looking for a flat or a room to let.

The most difficult part of establishing yourself in southern Spain may not be landing a job, but avoiding being exploited by locals. I've personally heard more than one Andalusian talk about buying an apartment with the sole intention of renting it at an inflated price to unwary foreigners, especially Americans, who they imagine are all wealthy. I strongly suspect that the result is that tenants from the U.S. and Britain, who often erroneously believe that anything outside their own country is the Third World and arrive expecting the worse, are often charged exorborant prices for miserable lodgings no Spaniard would accept.

In a nutshell: arrive qualified for the job, stay legally, be prepared to adapt to local concepts of what constitutes appropriate classroom behavior, either bring along a friend to split the rent or find a flat mate once in country (or have substantial savings on hand to help you make ends meet), and be wary of local proprietors.

¡Y buena suerte!