I took a standard 60 hour tefl before going traveling, and to be honest, it was a waste of money. I've a lot of friends who teach English as a foreign language. Some did it for the odd job while traveling, others do it professionally and long-term.
If you want to do this professionally, and plan to have some options about where you teach and what level, you'll need to take a CELTA course (possibly then followed up with a DELTA). These are internationally regarded as the best qualification. The downside is that they're substantially more expensive than a bog-standard tefl, but they're a much longer and more comprehensive course, and are widely regarded as a 'proper' teaching qualification.
Hope that helps.