Mckinney Falls State Park  5808 Mckinney Falls Parkway  Austin, Texas 78744  Adult $6  Things to Do.... Camping, hiking, mountain biking, road biking, picnicking, fishing and wildlife observation are popular activities. Swimming is allowed in Onion Creek; call (512) 243-1643 for current creek conditions.  Children 12yrs and under free  Open 7 days a week  8am-10pm