The U.S. Postal Service’s board of governors is set to meet tomorrow, according to a spokesman, and a thorny choice will likely dominate the agenda: Let Postmaster General Pat Donahoe proceed with a previously announced plan to end Saturday mail delivery this August, with a projected savings of $2 billion annually. Or back off—at least for now—to avoid a probable lawsuit, not to mention antagonizing members of Congress whose help is needed to pass any long-haul fix for the Postal Service’s finances. Among some observers, the betting is that the board will opt for door number two. “That’s the strong…