Flights on Aerovega and Aerotucan are about $125 USD each way, but sometimes there are specials so check. There is also regular bus and van service. On Calle Galeana there are about 3 different Transportes which have vans going and they're about 120 pesos ($11 USD) one way. There are other companies scattered throught the city as well. Take anti-nauseant meds with you and pop one about 40 minutes into the trip, if you sometimes are susceptible to that kind of illness. Highway 175 is the easiest although it takes longer than 131. If you can afford the flight, it's 35 minutes, goes over great terrain that you can always see below, and at least regarding Aerotucan, is reaonably reliable in terms of scheduling, perhaps moreso than the vans. Call from the USA at 01 800 640 41 48, or call the Oaxaca office at 52-951-5010530, or email at firstname.lastname@example.org. Weekday flights leave Oaxaca at 7 am. If the budget is really tight, then van one way, and if you didn't like the experience or stomach is weak, fly back. That way you get two very different experiences. Casa Machaya Oaxaca Bed & Breakfast.
Over Christmas we flew on Aerovega from Oaxaca to PE round trip for 2,000 pesos per person. That is around $90 US each way. It was a 10 passenger twin-engine plane. I flew in the copilot seat and the visibility was fine because I was looking through real glass. However, the other windows in the plane were plastic and had aged quite a bit so it was not easy for the other passengers to see what we were flying over. It was a quick flight, though, so it did not matter that much.
"Flights on Aerovega and Aerotucan are about $125 USD each way, but sometimes there are specials so check."
We waited until we arrived in Mexico to make out flight arrangements between PE and Oaxaca. Going through a local agent, we ended up only paying about $80 USD one-way for a two hour flight. The bus would have taken approximately nine hours (at best) and from what we understood was not called the "Vomit Coach" for no reason. All the locals we met advised us to just forget the bus and spend the extra money on a plane ticket. It sounded like it would be worth the extra $60 (bus tickets were around $23 USD) just to not need an extra day's recovery time from our commute.
If you're staying in Oaxaca City, check with your hotel to see if they can make flight arrangements or might know of some one who can in the area.
We were in Oaxaca City early Jan and took the van to Puerto Escondido. The van only cost about $15.00 USD BUT regardless of what anyone will tell you it did take 6 hours and it was CRAZY. I sometimes get car sick so I was sure to take motion sickness medicine and took a plastic bag just in case. I didn't get sick my one of my traveling companions did. You really couldn't enjoy the scenery from the van becasue you were too busy hanging on so you didn't get dumped off your seat. We flew back to Oaxaca City via Aero Toucan, it cost about $115.00 USD but man oh man it was worth it. The scenery from the plane was phenominal and only took 30 minutes. Yes it is much cheaper to take the van, but really you are losing an entire day of your vacation. We cut corners elsewhere. So, maybe a van one way and fly the other is the way to go. Have fun
If you have the money to fly, I would suggest taking that option. I have taken that van ride a few times and it is somewhat of an experience. The last time I took it (about 2 years ago) my traveling partner, who is succeptable to being car sick, tossed his cookies! We were about 5 miles from Pochutla and he blew chunks all over the back of some random Mexican guy! It was extremely embarassing, and my buddy felt really bad. So, if you are prone to motion sickness... Fly!
My buddy tossed his cookies on the van ride between oaxaca and pochutla. He blew chunks all over the back of this guy's head! It was embarassing... I would fly if I were you!
I took the overnight first class ADO bus for 240 pesos to Puerto Escondido last weekend. While a long trip (9.5 hours), it wasn't absolutely horrible. I'd definitely take earplugs and dramamine -- the driver liked to loudly listen to the radio at 3am and the road was a bit curvy.
On the way back, I took the 7 hour vomit coach (not first class). Again, I took dramamine beforehand and I didn't have any problems. It was much cheaper (130 pesos) and the road was much, much curvier. Sadly, I had the misfortune of sitting in the back middle seat and the person in front of me decided to recline all the way. I'll never complain about getting the middle seat on an airplane ever again.
To echo the comments of others, if you have the cash definitely take the plane. Otherwise, I'd suggest pickup up some anti-nausea meds at the pharmacy beforehand. I found the overnight first class ADO option more comfortable (but much slower and pricer) than the minibuses/suburbans.