User blog comment:Commdor/E3 Coverage of ME3 News Begins/@comment-2220462-20110610011837/@comment-2174252-20110611152704

Right… The first reference to a piloted mech was in the Spanish magazine article in mid-April. See Commdor blog from Apr 20:

http://masseffect.wikia.com/wiki/User_blog:Commdor/More_ME3_Details_from_the_BioWare_Forums