The Irving Soccer Complex is located at 3585 World Cup Way in Irving.  World Cup Way does not show up in Mapquest or Yahoo maps.  The Irving Soccer Complex is located off of Beltline just north of 161.

Take I35 North to TX-121.  Take TX-121/183 and merge onto TX-161 N - I believe this becomes a toll road after a few exits.  After a few miles, take the exit off of TX-161 toward Belt Line Road.  Go north on Beltline - you can see the fields from Beltline on the left.  Turn left into the fields (this must be World Cup Way).

The following is a original graphic from the Irving Soccer Association web site.  The complex is new so older MapQuest maps do not show the fields.