What a great adventure!
We moved to Oaxaca, Mexico 8 years ago. Our expenses are $1,600 per month which covers a family of four. This covers all expenses except housing (we own free and clear): tuition for two kids in private school, piano lessons, aerial dance lessons, housekeeping once a week, all fresh/organic/local produce, all (high quality) medical/homeopath and dental out of pocket, maintenance for one old car, utilities. In Oaxaca, no a/c or heating is necessary, so our bills are low. (Electric is usually about $12-$15 per month). Skype for int'l calls, about $8 per month for pay-by-the-minute dumb phones for local calls. Use the Schwab banking card to avoid all international transaction fees on cash withdrawals.
The surprise expense not covered here is travel to the U.S. With two young kids, we wind up going twice per year to see extended family, which adds up, but such is the cost of living a vacation-like existence for the bulk of the year. We drive usually to keep costs down and then stay with family when al norte.
I should add we live cheaply, moreso than other expats might. We eat local and fresh rather than replicate the prepared foods diet of many U.S. people. We only lightly drink and are vegetarians. Rather than join a gym, I dance Zumba in a local park and my husband runs in the mountains. We are budget travelers. We eat street food more than restaurant food. We go out all the time, but to free film festivals, street parties, ancient ruins, villages, parks, cantina concerts, art openings--very low budget.
In short, it's absolutely wonderful and I wholeheartedly recommend the path you are considering. Good luck!