Miley Cyrus & Patrick Schwarzenegger -- Let's Be Blunt About This ...

As the saying goes ... where there's smoke, there's Miley Cyrus -- and this time her bf Patrick Schwarzenegger was there too for a suspicious-looking toke break in Miami Thursday.

Miley and Patrick stood on a hotel balcony ... smoking his and hers blunts in plain view of cameras.
No way to tell from the pics exactly what they lit up -- so draw your own conclusions.

The couple's down in South Beach for the Art Basel show ... where clothing is optional. At least for Miley.