Caesars boasts the worst Starbucks in the city, or at least the worse one that I've been to. Slow is a concept here; they have one register open on a Friday night; one time there were 3 people hovering over a POS system for literally 15 minutes while angry customers stewed on line.
The counter girls actually yelled something at patrons (we couldn't understand what she said) as if it's ok to not serve anyone for 15 minutes while you figure out how to do your job.
There's another Starbucks at the Las Vegas Blvd entrance (downstairs from the walkway to Ballys/Horseshoe) that is usually not very busy. We recommend you try that one.