Guys I spent a few hours finding the best ways to get to the fields Sunday and here it is.
Whatever you do, DO NOT try to go down I-80 and approach the fields from the south coming up NW 48th St.
The best way to come is to get on Purple Heart Highway and turn left onto Woodlawn Road. That turns into NW 48th St. and will allow you to approach from the North of the fields.
You also can try to go down W O St., but it is a little backed up. (Do Not turn onto NW 48th there.) Go past 48th to NW 56th St. and take a right. Take that as far as you can down to W Adams St and take another right and that should drop you off pretty much by the fields (you'll have to only go through the traffic for like a block or so.
Here is a map: