Know Before You Go
Getting to the Monastery is a quick ride from Central de Abastos, or you can catch a bus (only 7 pesos) at the bus station at Calle Bustamante #601. Look for any bus that clearly says Zaachila on the front. It will take you through the Village of Xoxo toward the Monastery, which you really cannot miss. When done with your visit, you can jump on the same bus, in the same direction to get back to Oaxaca.
Plan on spending a few hours here. Walking shoes are advised. There are uneven stone steps, so take care when exploring. There is a 45 peso (approximately $2.50 USD) fee at the entrance to the cloister.