Master's to teach English abroad and back home.

I currently have an initial teaching certificate through the state of Oregon (Social Studies for Middle and High School to be specific). In order to renew/upgrade it, I must enroll myself in a Master's program that is GERMANE TO MY PROFESSION OF TEACHING IN PUBLIC SCHOOLS. Now, I like the idea of getting a degree, traveling (and teaching) abroad for a few more years and then returning to the states (not necessarily Oregon) to work as a social studies teacher with an endorsement (not to mention experience) with English language learners. Surely that would make me competitive in a state that is downsizing all their non-math and science teachers?

My brief research has lead to believe that TESOL is needed to teach abroad and while ESL training is largely expected for teachers on the West coast, getting an ESL endorsement would not be beneficial (or seen as beneficial) in teaching abroad like the way that non acredited TESOL programs are. I am also concerned that this experience being that it is outside of my credential, can not be used as "related experience."

Has any taught English in Korea and returned home to teach in a K-12 enviroment?

Please let me know what options are out there. All I want is:
1. A Master's Degree
2. Freedom to travel to find teaching positions
3. Related work experience and credentials to find a job in the United States after some time.

An ESL endorsement on your teaching cert would be helpful for teaching abroad, but it won't hold the same value as an MA of course.

MA TESOL is the ideal degree for teaching English abroad, but it certainly isn't the only degree.  Any master's in applied linguistics, education, or even English literature would be highly regarded as well.  An M.Ed. in ESL curriculum / instruction sounds like a good choice for you.

CELTA or an equivalent (Trinity CertESOL) means quite a bit abroad, but means nothing in the US.  Nonetheless, I highly recommend doing a CELTA just to better yourself as a language instructor. 

As far as experience goes, international schools would provide the most relevant work experience if you want to go back to teaching in the US later on.  Teaching in a hagwon or public school scheme is better than nothing, but still means very little. 

Good luck!