This is where one would hear the "Mission Impossible" theme music.
If you had said, "I don't want to drive more than 10-15 miles to get there", then there are a lot of options, such as PCH north or south out of Santa Monica, or Griffith Park. But close to downtown? It will be difficult to maintain 20mph because of all the commuter traffic and traffic signals. You won't get much of a ride. Good luck. Maybe somebody else knows a hidden gem in the area.