I actually think it is a fantastic building. Concerning the big blank walls, consider that is what is important about his buildings. Legoretta draws much of his aesthetic from traditional Latin American architecture, which favors the solid wall and strongly defined space over the open and airy aesthetic of modernism.
I'm no big fan of most modernism, but at the same time, there's some distance between "blank featureless wall 'o stucco" and "plate glass transparent." With the building on the street like that, I want to see *something* - smaller windows, some sort of detailing/trim, places for posters of exhibits, a mural, whatever.
I think once everyone has a chance to see the building in person, the experience will assuage the criticisms. Consider the big blank walls as part of the desired aesthetic, one that evokes the history of adobe and stone architecture of Latin and South America's past as well as an expression of color which is an important aspect of all of Legoretta's buildings.
The desired aesthetic shouldn't preclude the building from being so bleak at the street level, though. If it does, perhaps the desired aesthetic should be rethought.
EDIT: Looks in some renderings like the actual street level might be some sort of stone, which is an improvement. Something with texture, anyway.