Pros
I worked at the learning center in Cayambe, Ecuador at the end of 2011 as an interim English teacher. A fabulous atmosphere for interacting on a multicultural level, Wall Street English (used to be known as Wall Street Institute) offers employment to qualified English teachers. They prefer candidates who have taken an ESL course, but it is not always necessary. The learning centers are open concept, with glass partitions. The students (all adults) are typically highly motivated (they are paying to attend!) and courteous. Most are eager to learn not only English but facets of the teacher's culture. The staff is very friendly and accommodating.
Cons
You may be asked to work some evenings during the week as many of the students have jobs during normal business hours. Pay was based on normal wages of the host country. In the case of Ecuador, it was $500 per month. That is enough to survive, if one lives frugally.