It’s a pleasure coming in (and going through customs) in the small airport in Oaxaca. So, you might look for direct flights into Oaxaca — such as United’s direct flight from Houston. Usually, however, itineraries will have you making a connection in Mexico City (more flight legs, but sometimes for less money). A travel agent may be the best person to help you, as they still have access to low rates (even if there is a fee for the service). But you can also shop around on line for economical air tickets.
I had heard that Interjet had a direct flight from Orange County, California, to Oaxaca. But I just contacted them and they told me that one has to go through Mexico City.
Some former participants (such as those from California) have found savings by flying or driving to San Diego, crossing the border, and flying from Tijuana. That may entail a risk, and so it would be up to you. Volaris flies directly from Tijuana to Oaxaca. Roundtrip is currently around $450 USD.
Please plan on arriving in Oaxaca on or before Sunday, July 5. You might just want to figure on spending the entire month of July in Oaxaca. Some hotels have a monthly rate, so it might not hurt to add the first few days of July onto your itinerary (inquire if in doubt) and try to depart on August 1st (or after). If you come in early you will have a little time to get settled before the opening reception on Sunday. If you want, you could try to reserve your lodging from July 2 to August 2, to give yourself time to acclimate to Oaxaca before the institute starts and an extra day before you depart.
You can also travel to Oaxaca by bus from Mexico City. This will represent a savings over flying, but it will add travel time. The bus trip lasts about 6 hours (sometimes more). ADO is a good company for the trip to Oaxaca, which goes through Puebla and has dramatic scenery a large part of the way. You might wish to make the trip in the daylight for just this reason. To get on the ADO buses, which run about every hour, you can catch the bus from the eastern bus terminal, TAPO, in Mexico City. You can take a taxi from the airport to the TAPO (get a collective taxi at the airport — this is one where you purchase a ticket from a window in the airport, which is the most secure and also the most reasonably priced taxi). You can purchase your tickets for the bus ahead of time from the ADO website. Last year, roundtrip tickets cost 874 pesos (about $60 USD). Departure times from TAPO, probably subject to change, are currently at 8:30, 16:00 (i.e. 4 PM), 23:15 (i.e. 11:15 PM), and 23:59 (almost midnight). You will notice that it is very common in Mexico to see military time in lieu of the use of “AM” and “PM.” We will try to use this system, too, so that you will get used to it.