question about u.s cellular field and chicago in general?

Cellular field is on 35th and Shields .. on the South side and there is no Hotel/Motel within a safe walking distance.. how ever the Red Line stops at 35th and it is a block from the stop

the area around the Cell is not a safe neighbour hood to walk in alone after the ball game//

There are no hotels located near US Cellular Park. However, as it's only about 4 miles from downtown, you can easily access it via the CTA Rail Red Line. A few choices for downtown hotels would be the Hard Rock or the Hilton, both of which are right along Michigan Avenue, and near Millenium Park. Then just over the Chicago River you'll find a Sheraton or the Embassy Suites. And you'll be able to find numerous other choices within a block or two of the Red Line stations. From any of the hotels, you'd walk to the subway stations which are along State Street and take the train to 35th Street. From there it's a one block walk to US Cellular. It's a 10-15 minute trip depending on which hotel you might select. As to the rental car, skip the expense of both the rental car and the parking costs and spend that money on a few extra eats or drinks at the ball park.