It's a nine-hour bus ride from Huatulco to Oaxaca—that's including a stop for lunch but not including a stop to be boarded by the army looking for contraband. It's worth it. The trip itself, although long and tiring, passes through some beautiful, rugged country, and the city at the end is a jewel.
We saw the sights, visited museums, dined well, and took long, hot showers at the hotel. The temperature was just right, but sailors accustomed to the tropics need to remember to bring a jacket for the cool nights. If we could pick just one place in Mexico to return to, it would be Oaxaca.