How to Play Multiplayer on "Grand Theft Auto: San Andreas" for PS2by Nick Miles ; Updated September 22, 2017
In addition to being the last "Grand Theft Auto" title for the PlayStation 2, “Grand Theft Auto: San Andreas” was also the first GTA game to feature multiplayer functionality. There are various two-player icons spread across the "San Andreas" game map, which allow another player to join your game in "Free Roam" mode, meaning you can go anywhere you want and do anything you want.
Travel to one of the multiplayer icons on the map. Free Roam icons are located in Idlewood, Los Santos; Dillimore, Countryside; Kings, San Fierro; El Quebrados, Desert; and Royal Casino, Las Venturas.
Stand in the red two-player icon and then press any button on the second controller.
Select the avatar for the second player. You will have limited choices based on the location of the icon that you have selected.