San Andreas is an entire state, including the three cities Los Santos (Los Angeles), San Fierro (San Francisco) and Las Venturra (Las Vegas). Each of these will be bigger than the entire Vice City... The rumors say this game will be 4 to 6 times bigger than its predecessor... (I've already got low free space on my 280 GB, so I'll have to buy a new harddrive).
The gameplay will be early 90's, you will need to eat to stay alive, the building interiors will be improved, and you can commit burglary. You can run a Casino, or just gamble away your money in Las Venturra. You can recruit a gang, and drag members along on missions.
I can't wait to play this
The sources (contains more info than the stuff I wrote):
German: GameVision
English: Gamesradar
( I found both these on gta-action )


