Plainfield, along with adjacent Avon, and Brownsburg, and west Indy, have chains galore. Having said that, there are several good local places, including the ones mentioned above. They are:
Charbono’s, in Avon (US 36). Upscale-ish, probably not truely Roadfood, but very good, and locally owned. The same people also run the Boulder Creek restaurant in Brownsburg, to the northwest.
Big G’s BBQ. In a small house on US 36, just west of Raceway Road. Excellent BBQ, although sometimes a bit uneven in quality. Inexpensive, and worth checking out.
Papa Joe’s, also on US 36 (all of Avon is on US 36, and Avon is about 2 miles north of Plainfield). Classic red sauce local Italian. Pretty tasty, and cheap.
Thai One On. Again, probably not true roadfood, but very good, and local, Thai. The Mussaman curry and Pad Thai are heavenly.
I’ve also heard that Sal’s, another local Italian restaurant, has excellent pizza, but have yet to try it. They have a restaurant in Plainfield, on US 40 near downtown, and another in Brownsburg, on 126.
There are probably others I can’t think of off the top of my head, but that should be good for a meal or two. [:)]