From I-94, westbound from Milwaukee: west on I-94; exit onto Hwy 18. Take the "Waukesha-West" exit. You'll be on a 6-lane road for about 1 mile. When you start to see car dealerships, move into your left lane. Turn left on Hwy 164. It's another 6-lane highway which soon merges with Hwy 59 and forms a bypass around the south end of Waukesha. Stay on this road for 5 or 6 miles; St. John Neumann will be on the right just after crossing the Fox River, just before Highway X.
From I-94, eastbound from Madison: OPTION 1: exit on Hwy 164 and go south (right). This will become North Street; about 2 miles from I-94, it will curve to the left and simultaneously go down a hill in front of Mountain Village Apartments. At the stoplight at the bottom of this hill, turn right onto St. Paul Ave. Proceed about 3 miles to Hwy 59 on the outskirts of town; turn left onto Hwy 59 and left again almost immediately into the church parking lot.
OPTION 2: Exit Hwy 83 and go south (right) about 10 miles, to Genesee. Turn left onto Hwy 59 and head east for approx. 8 miles. Just after crossing Hwy X on the outskirts of Waukesha, the church will be on your left.
From I-43: Exit onto Hwy 164 and head north into Waukesha. When you reach the outskirts of town, there will be a stoplight at Hwy 59, which is a 4-lane highway at this point. Turn left onto Hwy 59 and proceed west. You will see the church on your right in about 2 miles, immediately after you cross the Fox River.