Alleyways, school or church parking lots with permission, find a friend with a lot of property and offer to let them ride in exchange. Or there is the highly non advised, it's only illegal if you get caught. In Colorado it has to be your own property, or private property with the owners permission to be legal to ride anywhere in the state. The law only shows up around my area if someone calls, I've been riding karts, buggies, mini bikes, dirtbikes, and the occasional drag car up and down the street for 20 years or so, I don't have many neighbors that mind what I do.