Take the Ashford-Dunwoody exit (one exit east of 400) and go inside the perimeter, away from the mall. The park is about 2-3 mile on your left, across the street on your right is a McDonalds.
non-285 ways to Blackburn Park:For those of you who can get to Clairmont Road - this is a great alternate route to Blackburn park. Clairmont Road (west) dead ends into Peachtree Industrial Blvd. Turn left and go to first traffic light (Johnson Ferry Road). Turn right on Johnson Ferry and go approx 2 to 3 miles. Make a right on Ashford Dunwoody - Blackburn will be on the right on corner.
Another way, if you're coming from downtown or Buckhead, is to take Peachtree St. northward, past N. Druid Hills, Brookhaven MARTA statiosm and Oglethorpe. 1-2 miles past Oglethorpe is Ashford-Dunwoody on your left, turn left, a few miles later this merges with Johnson Ferry Rd. and if you bear left, the park is about 200 feet on your right after the merge.