Starting July 1, the MBTA will not allow alcohol advertising on its property, including in subway cars, trains, and buses, a spokesman for the transit agency said yesterday. The change was announced as a bill to ban alcohol advertising on all state property gains momentum. In addition, youths from an Allston-Brighton-based substance abuse coalition spoke on the issue last month before Transportation Secretary Richard A. Davey and other T officials. In subsequent discussions, Davey and T General Manager Jonathan R. Davis agreed with the points raised by the group, said spokesman Joe Pesaturo. Pesaturo said the T’s advertising contractor, Titan, has told the MBTA that it expects ad revenue to decline by approximately $1.5 million in the first full year of the alcohol ad ban.