Unless restrictions have changed since last year, I think ATVers are restricted to stay on existing tracks/roads above 1700m. Motor vehicle closures are in place in the Lillooet area above ~1900m.

It's not uncommon to see atv's and dirtbikers making it almost to the first lake.

This is true, I saw both dirt bikes and ATVs just below the first lake. There is a small parking area there, where the ATV track ends.

were they recreational quaders or hunters? I heard the area is popular with hunters as well.

I only saw recreational quaders and dirt bikers, no hunters when I was passing through.

went up yesterday. just got back. No problems in a low clearance 2 wheel drive sedan all the way to the slide where everyone else parked. Lots of people up there. One group of 6-8 hikers tenting it at twin lakes. One group of quadders (one atv one side-by-side) one group of day hikers (to the cabin and back) and one pair of goat hunters.

4th option is to drive a good 4x4 to the end of the road below the 1st lake, or at least to the cabin.

The closure above 1900m is not for the entire Lillooet area, but for a few places north of Carpenter lake. The Blowdown road is easily drivable in a 4x4 to the Stein boundary at about 2200 m. Motorized traffic on the way to Twin Lakes is perfectly fine. It's not a park, nor there are any closures specific to it. Hikers simply like to think that as soon as they set their foot on a dirt road (which they call a hiking trail) it now automatically belongs to them, even though other recreational groups have used it for decades.