If you're looking for a break from Oaxaca's cultural delights and would like some downtime, maybe to enjoy some swimming during your stay, the best place is in San Agustin Etla. It's about a 20-minute drive from the Oaxaca city center, but it's well worth making the excursion. This swimming place has five pools, with a couple that are good for kids and one that is heated, as well as a couple of water slides. The setting is beautiful with great views of the surrounding mountains. You can choose a table near the pool of your choice and order drinks and food from passing waiters.
During Easter break and on weekends when the weather is hot, Vista Hermosa Balneario can get very crowded. For a quiet and relaxing time, head there during the week.