Huh? Are you saying that it would be a game based off of Los Angeles? Because, if that's true there's already a GTA game with the area Los Angeles. It's GTA: San Andreas, consisting of Los Angeles, (with the name, Los Santos) San Francisco, (with the name, San Fierro) and Las Vegas, (with the name, Las Venturas). Sorry, but it's already been done :/ .
By the way, with my spanish knowledge, "Las Altos" means "The Heights", which, in my opinion, doesn't exactly correspond with Los Angeles (The Angels).
As far as the art piece goes, the font needs to be a different color other than black. I can barely read it. Otherwise it's okay for GIMP, but if you begin to get serious into 2-d digital design, consider getting one of the older photoshops (CS or CS2). CS3 is simply too expensive for someone beginning to get serious.