I speak ok Spanish. It was good enough on my first visit to Mexico DF once.
Oaxaca is known for linguistic diversity given the high percentage of indigenous population. But it's also a pretty touristy place from what I gather.
Are there any perception issues regarding Spanish and the indigenous population of which I should be aware? (tension/conflict with central government, cultural issues etc)
Beyond the daily use to buy food/accommodation/transportation I'd really like to be able to chat with locals.