Are You Going to San Fierro?
Truth Mission: Are You Going to San Fierro
As you begin this mission, Truth explains that the police are on their way and that CJ needs to help him burn certain "vegetations" that Truth had been growing.
You obtain a flame-thrower so begin to burn the plants and make sure get every last one of them.
After you've burned all of them, a police chopper arrives and you'll have to shoot it down. Obtain the missile launcher from Truth's barn and shoot down the police helicopter.
Now, get into Sweet's hippie van and drive to the garage you won from Claude in San Fierro.