The word faded is often used as a slang euphemism for being high, or stoned.
In this case the phrase "let's get faded" would be an invitation to use an illegal drug like cannabis to get high. Although we've heard it used on the East Coast, it seems to primarily be slang that's used in Southern California.
The phrase was recently used on the TV series NCIS: Los Angeles; Henrietta 'Hetty' Lange says “I didn’t choose this life; it chose me. Keep your head down, gun up and conscience clear. The night is young; let’s get faded.”