From page 9 of Oaxaca Tips
Juárez House Museum (#5)
García Vigil 609, Centro
Daily except Monday: 10AM - 6PM
Entrance fee: 34 pesos

This was the house of Father Antonio Salanueva where Benito Juárez, Mexico's only indigenous president, lived as a boy and young man from 1818 to 1828. Juárez, a Zapotec Indian born in San Pablo Guelatao, was orphaned at an early age and brought to Oaxaca City by Father Salanueva to attend school. He went on to become the hero of the mid-19th-century Reform movement, a leading defender of the Mexican nation against the French Intervention, and one of Mexico's most revered presidents. The restored 18th C. adobe house features period furnishings and some of Juárez's personal possessions. The museum was founded in 1933.  Tel: 516-1860
From page 8 of Oaxaca Tips
Patio of Juárez House Museum
Museum of Oaxacan Cultures
Santo Domingo Cultural Center 
(#1)
Macedonio Alcalá (next to Santo Domingo Church), Centro
Daily except Monday: 10AM-6:30PM. Entrance fee: $48. 
Audiophones in English or Spanish: $50
Housed in the splendidly restored Dominican monastery of Santo Domingo de Guzmán, the Museum of Oaxacan Cultures exhibits the region's main archaeological, ethnographic and historical collections, including the Mixtec treasures from Tomb 7 at Monte Albán. This is Oaxaca's premier museum and not to be missed.
Santo Domingo Church
Entrance to Cultural Center and Museum is on the left
From page 7 of Oaxaca Tips
Ethnobotanic Garden of Oaxaca (#2)
Corner of Reforma and Constitución, Centro
Entrance is by guided tour only.
1 hour Spanish tour: Mon-Sat at 10AM, 12PM, 5PM   $ 50   
2 hour English tour: Tues, Thur, Sat at 11AM     $100
Housed in the former field area of the Santo Domingo monastery, the superb Ethnobotanic Garden displays an extensive collection of native plants of the state of Oaxaca. Whether you count yourself a plant-lover or not, the Garden is an enchanting place to visit and offers visitors an opportunity to learn about the amazing biodiversity of the state and the cultural importance of its flora.
Tel: 516-5325, 516-7915

The adjoining Ethnobotanic Library houses a sizeable collection of books about plants and gardens, many in English, and is open to the public. Mon-Fri: 9:30AM-7PM. Sat: 9AM-1PM. Entrance is free.
Also part of the complex is the splendid Francisco de Burgoa Library containing books and documents dating from as early as 1484. The core collection comprises books from the colonial monasteries and convents of Oaxaca, expropriated in the 1860s and donated to the Institute of  Sciences and Arts (the precursor to the present state university). Temporary exhibits with a historical or cultural focus are often featured in an ante room.

The Cultural Center presents art exhibits and occasional concerts.

The up-market museum shop off the main cloister offers a selection of Spanish-language art and archaeology books, as well as jewelry, clothing and folk art from various regions of Mexico.