The good thing about Ryan Field is the Purple Line goes really close to the stadium. If you want to go to bars in Evanston, there are a a few options. No Hawkeye Bars of course, but some decent bars.
I go to Tommy Nevins, and it is pretty good.
Prairie Moon is next door, and it has a better selection, but isn't much or a sports bar.
Other bars are Bar Louie (good food) and Celtic Knot (which is really close to Ryan Field)