If you drive to the trail from the north, take 1-90, and take Route 25 south to Elgin. Route 25 runs along the east side of the river, and Route 31 along the west side. The washrooms along the trail general do get locked up in the fall to late spring. The water fountains also are not on during the off season. One is really not far from civilization to find washrooms along the trail.
Food is available right off the trail within a block or two in all the communities along the river.
During peak season there are food stands along the trail itself. My group, the Fox River Trail Runners, hosts the Fox and the Turkey on Thanksgiving Day in Batavia. We presented the first annual Great Western 30k in St. Charles in May, which runs on the Great Western Trail. In this inaugural year we had 250 athietes. We had a great response to the event and the distance.