Action Comics 250 (March,1959) marks Weisinger's debut as Editor. However, the same link contains a link to the Grand Comics Database in which Weisinger is credited as editor as early as Action 230 (July, 1957). Actually, their credit for editor reads as follows for that issue:
Whitney Ellsworth (credited); Jack Schiff (managing); Mort Weisigner (actual)
The link above addresses the seeming discrepancy and is worthwhile reading for anyone following this thread.
As an addendum to "all the Superman titles": later on Weisinger took over as editor of World's Finest (from Jack Schiff) starting with World's Finest #141, cover-dated May 1964.
Weisinger wasted no time in making over WF into a Weisinger-Superman type of book: he immediately started using Superman writers like Edmond Hamilton on the main feature and handed over the art reins to Curt Swan.