Here in the 1852 LDS edition, men was originally mis-set as man. But in the second printing of this edition, the correct men was restored, either by reference to the 1840 edition or by noticing that the surrounding text uses the plural pronouns they and them. The critical text will, of course, maintain the reading of the original manuscript: “therefore God conversed with men”.
Summary: Maintain the plural men in Alma 12:30, the reading of the earliest textual sources (including, in this instance, the original manuscript).