[DaveESL]

I don't know much about certificate programs, but I can tell you a bit about MA programs. MA programs in the US usually take 2-3 years to complete. There are a bunch of different titles (MA in TEFL, TESL, Applied Linguistics, Second Language Studies, etc.). I just did one at the University of Hawaii. Many of them offer graduate teaching positions with a tuition waiver and a stipend. An MA degree is not necessary for many jobs, but some countries (Japan, Taiwan, etc.) require them for university jobs. International schools tend to favor them, too, as do a lot of Middle Eastern countries.

TOEFL is a test of people's English ability and is not required for native English speakers interested in a TEFL certificate. MA programs will probably require the GRE, though. And getting the training in the US is probably OK.

If you simply want to try teaching abroad, though, you don't need any sort of degree. You can get a job in many, many countries with just a BA. I'm not sure how many doors a certificate would open up, but I wouldn't recommend getting an MA degree without first seeing if you like teaching.

Hope this helps!
Dave