It varies here from state to state; in New Mexico you're required to have an ATV titled and registered if you ride on State or Federal land, they give you a motorcycle plate and the registration is good for 3 years. Technically if you never ride on public land you don't have to have it registered, and farm/ranch use doesn't require registration. I've been riding here for years and never been checked, and almost all the riding & racing I do is on BLM (Bureau of Land Management) or USFS (Forest Service) land. Both of those agencies maintain riding areas in NM, BLM OHV areas typically charge $3-5 a day to ride (designated OHV areas have at the least a parking area, porta-pottys and covered picnic benches), but there are many many more riding areas that are under BLM that there are no fees; the only catch is that BLM will sometimes lease the land to ranchers and they will fence it off (and get a little pissy about you being there if they see you, although being BLM land it's not really trespassing). USFS keeps up some trails in the mountains, and they split them up for hikers, bikes, quads, horses, etc., some are restricted to hikers only or way too narrow for quads. You can ride a quad on any USFS roads legally, which is lotsa fun...