Activist Tony Yapias, of the advocacy group Proyecto Latino de Utah, says he launched the campaign with his own letter to Monson.
Besides letters, Latinos plan to wear ribbons signifying unity in their quest to have the man Mormons regard as a prophet speak up unambiguously on what they see as a moral issue.
"This is affecting our families," Yapias says. "Where's the church in this? The longer they stay quiet, the more political it gets, the more divisive."
Sandy resident Alfredo Gallardo says he, too, is writing Monson to express what many Latino Latter-day Saints feel.
"There is a double standard now -- one for Sunday and one for Monday through Saturday," he says. "We want to write to the prophet to say the feelings of brotherhood have to be followed all the time."