SGWA issues the wilderness permits and monitors wilderness usage.
As far as I know there are no clear cut cross country route rules.
Traveling cross country routes or off trail can be very difficult thus it is kind of left up to the experience traveler to interpret the rules.
1. To travel in the San Gorgonio Wilderness requires a permit.
2. There are no fires allowed anywhere in the San Gorgonio Wilderness.
3. You can’t travel in any current fire closure areas unless there an exception.
4. Camping must be 200ft or more from any trail or water .
5. You must have shovel or hand trowel in possession for use in burying human waste during overnight camping.
6. No Shortcutting a switchback or mutilating, defacing, removing, disturbing, injuring, or destroying any natural feature. (Minimal Impact / Leave No Trace other than foot prints)
7. Must give a starting trailhead and exit if different.
8. Camping in a location other than that specified on the Permit. 36 CFR 261.10 (k) and 261.58 (e).
You should try to get a San Gorgonio Wilderness permit by writing in a camp location area that you plan on. But you won’t be allowed to camp in any other permitted designated camp sites.
If you have trouble with approval then select a permitted designated camp site nearest your destinations with the thought you could go there if you needed.