I went out there by myself in May 2017. I arranged permission to enter the ranch via Don Schmitt, founder of the Roswell UFO Museum; although there are no “No Trespassing” signs on the gate. It takes about 1.5hrs to drive out there from Roswell, the roads are great, even the dirt ones with the exception of the last mile. You don’t necessarily need a 4x4, just something that will have good ground clearance, I had a 2x4 Nissan Frontier, the large wheels made it easy to get over the rocks on the last mile of the trail; you can always walk it.
There is cell reception in certain areas of the site, I even did a live FB video; it is very spotty though. I noted the areas of cell reception just in case I needed to make a call. I would also recommend some kind of GPS tracker like a Spot, that way you can have a programmed message if you get in trouble or just to check in with someone to tell then you’re ok.
It is an incredibly desolate quiet place despite a few cows and farm buildings you’ll see in the distance. I spent about 3 hrs walking the site and collected some soil to take home. It was very windy.
Have fun exploring.