There are many ways to reach Mingo Creek Park.  The preferred ways involve using Sichi Hill Rd, Chapel Hill Rd, or Mansion Hill Rd from PA route 136 and coming in from the south.  Note:  Mansion Hill Rd ends by crossing a covered bridge; Chapel Hill Rd  ends by crossing a  bridge; and from Sichi Hill Rd you need to bear right onto Sugar Run Rd briefly and then turn right into the park.  The event is at shelter #5; the best  entrance is to use Chapel Hill Rd and turn left when it meets Mingo Creek Rd. You can see a map at  http://www.wpoc.org/mingolocator.pdf

Here are some suggested approaches to route 136.

From Pittsburgh, go south on PA route 51 or PA route 88 or US route 19.
On route 51, go south past Jefferson Hills to the end of Turnpike 43 (exit 54), enter theTurnpike and go south to exit 44 (route 136).  Follow 136 west past Ginger Hill to one of the three streets mentioned above; turn right and enter the park.  There is a toll for using Turnpike 43.
On route 88, go south past Bethel Park and Finleyville until you cross under Turnpike 43, then bear right onto Gearing Rd.  After about 0.5 miles, turn right onto route 136.  Follow 136 west past Ginger Hill to one of the three streets mentioned above; turn right and enter the park.  The map shows another possible route using Venetia Rd, Sugar Run Rd, and Park View Rd from Finleyville.
On route 19, go south past Upper St. Clair and Murry Hill to route 519.  Turn left on route 519 and follow it 6 miles south to the town of Eighty Four and route 136.  Follow 136 east to one of the three streets mentioned above, turn left and enter the park.

From the northwest, follow I-79 south past Canonsburg to exit 43.  There,  take route 519 south 7 miles to the town of Eighty Four and route 136.  Follow 136 east to one of the three streets mentioned above, turn left and enter the park.

From the west, follow I-70 east to esit 25.  There, take route 519 north 2 miles to the town of Eighty Four and route 136.  Follow 136 east to one of the three streets mentioned above, turn left and enter the park.

From the east, follow I-70 to exit 32A (route 917), follow that five miles north to route 136.  Follow 136 west past Ginger Hill to one of the three streets mentioned above; turn right and enter the park.  You can save about 5 minutes (at the cost of $0.70 or whatever the turnpike is charging now) by taking exit 37 from I-70 and following Turnpike 43 north nine miles to exit 44 (route 136).

Here is a Google maps link to  the end of Chapel Hill Rd (about the middle of the park)
We use various shelters; follow directions above or watch for orienteering signs.

The GPS  coordinates are 40.196252 N, 80.036302 W