Hello Steven :-) I'm not sure which postings you are referencing regarding getting shot at. I did make a recent comment in one of my post about snipers being helpful in solving the illegal ORV problems around Deep Creek and DCHS. I was joking about that of course :-) Also I haven't heard of any reports of anyone doing something like that. There were some vehicles that had windows shot out, but that was years ago.
Regarding the route you spoke of as a way to get legally closer to DCHS with a vehicle, I have hiked pretty often in the past along a ridge that lies between what you speak of and DCHS, and the terrain is such that you would be actually farther from the springs than anywhere you could legally park on the north side of DCHS. There used to be a 4x4 road many years ago that cut off of HWY 173 near the bridge where it crosses Kinely Creek. This dirt road ( very rough ) went along a higher ridge all the way to a point at the top of the hills just above and east of DCHS. This road was closed and is illegal for ORV traffic. There have been no signs of ORV's for many years in that area. The Squints Ranch route you speak of puts you way east of this old road, and it roughly appears to me from what you describe, that you would either have to hike down the hills to the PCT in the Deep Creek canyon, then in a downstream direction towards the springs, or you would hike eastward, which I think would run you into the Willow Creek canyon, then you would go back up and over another large ridge before reaching DCHS. I have studied the maps on numerous occasions before to try and ascertain the same thing you are trying to do and believe me, there is by far no shorter distance between DCHS and a legal place to park than off the legal Public Routes on the north side of DCHS. The USFS and BLM just recently changed all the route numbers so I don't know the new numbers yet.
You mention seeing someone carrying a helmet coming back from the springs. There are a number of places where illegal motorcycles and quads riders do get closer to DCHS. On some occasions I have even seen motorcycles at DCHS, they accessing the area by either the Bowen Ranch trail, and even the PCT. I have never seen a quad at DCHS. I just spoke with the USFS enforcement ranger Brad Burns this morning. They are doing what they can given what manpower and resources they have to address the illegal ORV problem in the area of Deep Creek. Of course they have a long list of things to address regarding thier many duties, and therefor can only do so much. They would cite quickly anyone caught illegally riding ORV's in the area. Also various visitors will take pictures and turn in information to the USFS regarding illegal ORV riding.
So your best bet is to get the up-to-date maps from the USFS and BLM on what roads and moto trails ( I don't think moto trails are legal for quads ) are currently legal to use, and stick to these trails. All the other trails you see are illegal trails. Hey I'm not as young as I used to be so I go to the closest place I can legally get with my truck to DCHS to make things easier on myself, and I also pick up trash when I go to the springs so being closer helps in this regard too. In 25 years of going to DCHS, and in hiking to the springs from all differant sides, clearly the closest and easiest place to legally park is on the open routes to the north of DCHS. These routes can be accessed off the end of the Bowen Ranch Rd, or off off of Deep Creek Rd, then on to the power line rd leading up into the hills. In your case, the location that would most likely offer you the best place to park, with the easiest hike to DCHS would be at the USFS parking area, which is located just south of the Bowen Ranch, just adjacent to the Bowen Ranch trail that runs from the ranch parking to DCHS. Of course there is no way to be sure that your vehicle would be safe from vandalism. Tampering with vehicles is a possibility no matter where you park out there in the open country. Definitely bring any maps with you as the area roads can be confusing. Good Luck :-)