Like many museums in Oaxaca, this museum is open at night as well as the daytime. One can stroll around town to the Zocalo and then down Independencia and up to Morelos and visit this museum, as a nice break. The exhibits are of many prehistoric artificants from throughout Mexico, not only from Oaxaca. There are descriptive cards at each room, in English as well as other languages, for the items on display. The entrance fees are inexpensive and if you like archaeology, this is a museum worth seeing. The displays are well done and many items are exquisite.  Most museums in Oaxaca ask for you to leave your backpack or other carrying items while inside. You receive an ID marker to retrieve it later. Everyone seems very conscientious about the safety of your items. (But if you are worried, leave the backpacks and other bags at your room.) Usually cameras are allowed in, although flashes may not be allowed.