In "The Man to Send Rain Clouds," what evidence suggests that the Laguna move in the two worlds: that of the Christian workers and that of their traditional culture?

The overlap—and indeed, the struggle—between Native culture and Christian culture forms the backbone of this story. It begins with Leon and Ken finding their dead grandfather, Teofilo, and taking him home to be buried. On their way home, they run into Father Paul, the Christian priest, who asks if they found their grandfather. They say yes but omit the important detail of his death. They do this because they do not want him to be buried in a Christian style, but rather in a Laguna style.
Later in the story, during Teofilo's burial, one of the other grandchildren asks Leon if he will fetch the priest to sprinkle holy water on the grave. Leon is wary of this idea, but he does it anyway. This interaction shows how they exist in both cultures, with both of these characters prioritizing aspects of the two cultures in different ways. At the end of the story, though, Leon is okay with mixing the two types of burials, saying that "now the old man could send them big thunderclouds for sure." Despite wanting an Indian burial, Leon accepts a melding of the cultures, even connecting the holy water to Laguna afterlife traditions.
So, the two worlds that you ask about are mainly reflected in the two ways of burial discussed in the story. On the surface level, though, we could also look at Teofilo: the story goes out of its way to mention his Levis and then later mentions moccasins that he made, showing that he too moved between these two worlds.