Tom:
1. There is one trail mileage that I think should be checked. The old San Gorgonio Wilderness Assoc. mileage diagaram,
http://www.sgwa.org/map2.htm, shows the distance from the Aspen Grove TH to the junction with the trail coming in from the Fish Creek Trail Head as 3.0 miles as does your 2006 version of the SG Wilderness map. Note in the SGWA diagram the bend in the trail about 25% of the way to the junction with the trail from Fish Creek TH. This bend is where the current Aspen Grove TH is located. The old diagram reflects a TH which is no longer there. Given the relocation of the trailhead, I think that the mileage from the Aspen grove TH to the junction with the trail coming in from the Fish Creek TH should be re-checked. NOTE: Your map shows the Aspen Grove TH in the correct spot.
2. The trail heading west from the current Aspen Grove TH does go down Fish Creek a ways, but it to my knowledge no longer goes through to the Santa Ana River area. I have personally tried to follow it to no avail. I talked to some horsemen recently. They had also had the same experience. Further, I recently signed up for a Sierra Club Trip. The leader discussed using the trail from the Santa Ana River, but then wrote us later that he had been advised that said trail no longer goes through. You might want to give that one a look.
3. Several of the trails in the Aspen Grove/Santa Ana River/Big Meadows/Coon Creek area don't have mileages posted on them. I'm not sure that is necessarily a problem, but I thought I'd mention it.
4. This is really minor, but your 2006 map shows Alger Creek Trail Camp on the east side of Alger Creek. In reality the TC is on the W side of the creek. This may be too minor a point to trifle with. At least you don't show the TC on the top of the next ridge to the east as does the USFS issued "Guide to the SG Wilderness."
Hope this is helpful,
HJ