Does random plasma glucose of 185 mg/dL = diabetes?

No.

The ADA defines diabetes as one of the following which must be reproducible on subsequent testing:

• random plasma glucose > 200 mg/dL in the presence of diabetic symptoms.
  
• fasting plasma glucose > 126 mg/dL
• 2 hour plasma glucose > 200 mg/dL with oral glucose tolerance test
  

Source

McCulloch, D. "Diagnosis of diabetes mellitus" Up to Date. May 2009.