A Russian development team is currently working on an ambitious fan-port that recreates part of the San Andreas map within the GTA: Vice City Stories engine. While impressive, it is an unfinished mod, not the full game. Available Alternatives
Websites claiming to offer a "PSX Eboot PBP" of San Andreas are misleading. San Andreas was a PS2 game, not a PS1 game; therefore, it cannot be converted into an Eboot (a format exclusive to PS1 games playable on PSP). Fan Projects: Gta San Andreas Psp Eboot Pbp
Boot your PSP. Navigate to Game -> Memory Stick . You will see the GTA San Andreas icon. Launch it. A Russian development team is currently working on