Hi Cleet, i finished the "drive by" mission yesterday, failed the next one where you have to rescue Sweet and spent hours exploring the landscape freely. I swam across a large waterway and ended in Vinewood and stole a badassed Infernus. Swimming kicks ass and i'm loving the bicycles too. I also swam somewhere where i instantly got 4 stars and had the cops after my ass.
You're right, i can't believe how huge GTA:SA is....downright amazing.