The U.S. Secret Service does conduct drone exercises, but the specific locations of these exercises are not typically disclosed for security reasons. However, it is known that Washington D.C. is a highly secured area with many no-fly zones, especially around critical infrastructures and government buildings. Therefore, it's plausible that some training or exercises could occur in the vicinity, but it's also likely that many exercises take place in more controlled environments or designated training areas.
In 2015, the Secret Service did publicly announce they would be conducting drone exercises in the D.C. area late at night to test their own detection capabilities and response protocols. This was in response to an incident where a small drone had landed on the White House lawn.
However, such public announcements are rare and usually only made if they anticipate the public might notice their activities. In general, details about when and where these types of security exercises take place are kept confidential to maintain operational security.