Justin Bieber -- Adios South Beach

Citizens of South Beach, you can now resume your daily activities ... Justin Bieber finally left Miami -- but not without a ton of fanfare.

Biebs tried leaving his rented mansion Friday night ... but when security couldn't clear a path through a throng of screaming girls ... his people were forced to turn Justin around and sneak him out the back.

As we previously reported ... police claim Justin may have been drag racing when he was arrested Thursday ... but cops may have goosed the facts to justify the stop.