According to
Tuttograts, the head of Theatrical Distribution for Walt Disney Italia, Stefano Bethlen, has revealed that the star-studded cast of Marvel's superhero extravaganza
The Avengers will assemble in Milan, Italy to accommodate the highly-anticipated film's international premiere. Read the [Google Translate] excerpt below for the so-far available specs.

The [event] in Italy is scheduled for April 25, 2012 Professional Days and from Sorrento currently an announcement that the premiere of the film touches Milan with interpreters present to the delight of many fans.
The cast members who will participate should be nine, but [we] obviously [have] yet to know the names. It 'was Stephen Bethelen head of distribution at the news that the cast of the film will be on the red carpet Milan ready to sign autographs for fans glia. In fact at first the event was announced in Rome, but then there was a counter-ad with the correction of Milan. For now you just have to wait for further developments and news about this great event which certainly will block traffic for a day of the Madonna of the city. Stay tuned!
We also discover that Milan will [have] the official launch with a special event organized by Disney Italy, the 'Marvel week' in which there will also be attended by a number of initiatives and actors interpret the Joss Whedon film that brings together the Marvel superheroes, from Black Widow Captain America in an adventure that will involve them all.
With previous
reports of there being a star-studded premiere in Moscow, Russia, Disney is seemingly making an effort to have the flick's cast members attend multiple international premieres, in addition to the U.S.'s worldwide red carpet event. Also, I'm not too sure what to expect from 'Marvel Week,' as mentioned in the 2nd quoted paragraph, but the best thing about all this early "premiere" talk is that we're getting even closer to seeing the movie; with an approximate 4 months & 30 days remaining.
Marvel's The Avengers is the Super Hero team up of a lifetime, featuring iconic Marvel Super Heroes Iron Man, The Incredible Hulk, Thor, Captain America, Hawkeye and Black Widow. When an unexpected enemy emerges that threatens global safety and security, Nick Fury, Director of the international peacekeeping agency known as S.H.I.E.L.D., finds himself in need of a team to pull the world back from the brink of disaster. Spanning the globe, a daring recruitment effort begins. Starring Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Jeremy Renner with Samuel L. Jackson and Tom Hiddleston, directed by Joss Whedon, Marvel's The Avengers will be released May 4, 2012.