Hola I am from the US and visited The Museum of the Revolution about half a year ago. It is located directly across the Plaza de Armas from the Cathedral in Leon. Sorry, I do not know the address. Originally the building was a public utility office. During the last days of the Somoza regime, the building was held by Somoza's army and heavily contested as noted by the many bullet holes in the building. The Somoza family, father and two sons, ruled Nicaragua from 1936 until 1979. As I recall, Leon was the first major city to be taken by the revolutionary army, the Sandinistas, about 1979. The museum tells the story of the revolution starting with Augusto César Sandino's contribution, his death 1934 by the National Guard and the sequential rise of the FSLN (Frente Sandinista de Liberación Nacional). The FSLN was named after Augusto César Sandino. The museum is run by a group of Sandinista veterans who guide visitors through the museum explaining the various artifacts and the history behind the revolution. Our guide fought for the actual museum building and his entire family died during the revolution.

We went to the museum on a Sunday, so as far as I know it's open 7 days a week, probably in the 8:30-5:30 range but I can't confirm that. I believe getting some payment to be guides at the museum are how these revolution veterans make a (small) living, so they're highly motivated to be open whenever possible!