That was discussed a while ago. I'm pretty sure that's a phone number on the billboard - as in "advertising space available, call this number if interested." Maybe it will be released on that day, but I don't think the billboard is showing the release date. I don't know; it doesn't look like a date to me. The first two numbers look like 70, and the area code for Las Vegas is 702...
June 6th actually seems kind of believable since the mini site is already up. All we need is the map and a second trailer
Attempt one: Pawn Shop. Attempt 2: "WHO ARE YOU PEOPLE?!" Attempt 3 "Pizza" I am not trying after attempt four. Nor will I mention it again
I took that hidden map image from the background and adjusted the colours so we can see it a little better.
Another site claims June release & Gangstar City (java) was launched today by Gameloft "The release is scheduled for June, but an exact date is not known yet."