Boulders is lots of up & downs, tight turns and terrain can be get pretty rocky. 4x4 for sure is needed in some areas. You can do the loop which is what most people do or go west towards wickenburg. a sxs is what i would recommend to bring to enjoy it at its fullest, can still be done in a jeep but at a much slower pace and weekends on the cooler months bring a lot of traffic to this area.