There aren't too many places to ride that are "legal" in that area. Haspin, Perry State, and Wayne National Forrest are your best places.
There used to be a spot in some town south of Middletown you could ride. The electric company owns a bunch of property by the Miami river and there are trails and a small track back there. I think the town is Trenton or something. I've been down here in TX to long to remember accurately.
There is also another spot in Dayton. It's close to downtown and near Honda of Troy. If you go up to the shop you might be able to probe one of the guys for more info. All the land there has been escavated and I believe there is a dump site there aswell. Its full of sand, hills, and trails. It's somewhere around 30 acres, not big but it was decent for being 5 minutes from my house back then.