With the exception of Sly, every other person was in a previous Spy Kids or other Rodriguez film and he seems to evoke a lot of loyalty from the actors he works with. they'll show up and do whatever he asks them to.
Antonio and Salma have been in so many of Roberts movies since the mid nineties. Elijah Wood was in The Faculty, and then later Sin City. Buscemi was in Desperado and Spy Kids 2, etc.
Perhaps the biggest coup was George Clooney, who was also in the two previous Spy Kids, but Robert also helped make him into a movie star in From Dusk Til Dawn.
Robert works fast and effeciently. I would be surprised if any of the stars worked for more than a day on the movie and they more than likely were only one there on the set.
I think it speaks of Robert in a very positive way, in that all these actors keep coming back to work with him, especially in a movie of this quality