Anyone traveling out West in October needs to be aware of the
Santa Ana winds. When a high pressure area builds up over the Four Corners area (Utah, Colorado, New Mexico, Arizona) some pretty vicious wind condition can develop. They concentrate in Southern California but high winds can be expected anywhere in the region.
Freeways are often times closed - usually after a few 18 wheelers are blown over. So keep an eye on weather conditions and build into your travel schedule an extra day or two.
If you do the Las Vegas side trip you will pretty much be committed to continuing west on I-15. Nothing impressive about that route but if by chance you decide to skip Las Vegas then consider doing a side trip south down into Lake Havasu City on Arizona route 95. It's a nice place to check out and with some pretty good boondocking all through there. And the drive down the river for a ways past Lake Havasu to I-10 at Blythe is pretty nice most of the way too.
Over past Palm Springs, then, you'd want to take route 60 at Beaumont over to the I-215 and on south down to San Diego.
For a real nice stop 30 miles east of Flagstaff check out the
Meteor Crater at exit 233 on I-40. They also have a quiet little campground there.
Half the fun is in the planning, they say. Good Traveling.
edit: links check?