Travis County Sheriff Sally Hernandez Invites Reports About Narcotics, Prostitution, or Organized Illegal Gambling.

https://www.tcsheriff.org/vice-form

"VICE 
"The Travis County Sheriff’s Office VICE Unit is tasked with investigating the possession, manufacture and trafficking of narcotics, and certain types of human trafficking, prostitution, and organized illegal gambling. If you have information related to any of those types of crimes, we encourage you to relay that information to us by calling the VICE Unit Tip Line at (512) 854-7425 or via the form below.

"The phone and email tip lines are usually checked by VICE Unit Investigators on a daily basis during regular business hours. Tip lines are not generally checked on weekends or holidays. If your situation is not an emergency but requires an immediate response from our Patrol Division, please call the TCSO non-emergency dispatch line at (512) 974-0845. If you have an emergency, please dial 911." 

If you observe evidence of illicit-drug activities, prostitution, or illegal organized gambling WITHIN the city limits of Austin, this Travis County Sheriff's Office webpage does not specifically state that you are expected to call the Austin Police Department in that scenario.

 It is possible that the Travis County Sheriff's Office will be willing to investigate some cases, at least, that occur in Travis County within the city limits of Austin. I plan to call the Sheriff's Office to obtain clarification on that point.