The main roads are east-wests '''I-90/80''', which runs from Illinois to Ohio through South Bend and Elkhart, and '''I-69''', which runs up from Indianapolis to Michigan through Fort Wayne. Both are very convenient traveling roads throughout the region, with high 70mph speed limits, and light traffic.
The '''South Shore''' line runs straight to South Bend through Northwestern Indiana from downtown Chicago.
It's by far easiest to travel through the region by car. The aforementioned highways are the main routes, although US Hwy 33 is a very convenient way to get between Elkhart and Fort Wayne.
Northern Indiana is very rural, and is worth exploring, if only to see the natural beauty of the state.