A bit late of a reply, but here's my advice: buy an atlas that shows land ownership. BLM lands are usually fine for dispersed camping, as long as you're not in a specially protected area, such as a recreation area (which will have picnic tables, signs, etc) or wilderness area or national monument/national conservation area. BLM lands hardly have any rangers (like, say 1 per 500,000 acres) and you're much less likely to see anyone out there than on any of other lands. Forests would be a good backup.