I am thinking that no mosaic can be called "graffitti".
Most graffitti here in Miami consists of illegible, purposefully ugly scrawls, made by dolts marking territory like tomcats spraying on trees and fence. In Spain and France, I saw a lot of that as well, but along the train tracks, there were some amusing cartoons that were clever and rather artistic. We have had only a little of this in Miami.
I agree that this is not graffitti,and it would be best just to legalize it, as they did with the Watts Towers and Carhenge.
I question the premise that the Virgin of Guadalupe is a surfing type, but the mosaic unifies a Mexican icon with a surfing icon and should get an A for artistic.