I've attempted Skull Mesa twice now. Once was with another guy who took us the longest and most difficult route possible so by the time we got to the base I was crushed and didn't do it.
Today I took trail # 4 all the way to the far end of the northwestern part of the base. Just below the ruins. I was told I could climb up the backside. Not in this lifetime!! So next weekend I take Cottonwood trail to Skull Mesa and ascend her.
I give it 4.25 - 5 stars. Nicely challenging!! Gorgeous scenery. I Recommend wearing hiking boots rather than running shoes. Boots will give you better traction (that you'll need) and keep you from turning an ankle. Super rocky in spots, but GORGEOUS views (although I recommend that you stop to take in the views, as it's too easy to turn an ankle or trip if you enjoy the scenery while moving). I posted some pics. Took my dog, but keep an eye out for fallen Jumping Cholla cacti because you don't want to remove them from your friend's paws. Most of them I could kick off the trail, but there was one area that I had to carry my dogger because they covered the entire trail.
I know the secret to finding shade on this trail! I hiked Elephant Mountain twice in one day on the last weekend of May - at 8:30AM and 3PM (Sunrise 5:18AM; Sunset 7:31PM). Both times I took Spur Crossing/Tortuga/Elephant Mountain. On the morning hike, there was virtually no shade at all. On the afternoon hike, there were many long stretches of shade particularly after the 3-mile saddle crossing. There was a bit of a breeze that even made it feel very cool in the afternoon shade on the 93 degree day. I hike pretty fast, and easily completed the hike in 3 hours. I did not see the ruins. :( I saw only a handful of people on the morning hike; not a single person in the afternoon. Note that of the 7 mile hike, only the 2 miles of Elephant Mountain Trail are rated difficult; the rest of the hike is moderate; since I like difficult trails, that was a slight negative, but still a 4-star trail for sure. Many gnats and flies followed me around in the low areas, but didn't bite. Incredible desert views from the high points on the trail make this well worth a visit.
30 minutes from home and only saw 5 people on the entire Elephant Mountain loop on s Saturday. Be sure to gaze at the ruins as you pass through the saddle. Total hike was 7.5 miles from where we parked. Green grass and large cacti in some of the washes. Ocotillo were blooming on 30 Jan in one place. We will go again--3 bucks is very reasonable just don't forget cash. Also, we were fooled by some parked cars just before the actual parking area, so keep going!
To get to the trailhead, park at the Spur Cross Conservation Area and hike north (right) on the Spur Cross Trail. Once the trail crosses into the Tonto National Forest, it changes to FS 4. Continue until you reach a fork at an old corral. Take the right fork and continue hiking. You'll eventually reach a large National Forest sign that says Skull Mesa Trailhead on it. It should take about 40 minutes to reach the trailhead by this route.