The trailheads close to the SG Valley are very popular with hikers during the weekends, especially Lower Sam Merrill. I think LSM is one of the most traveled trials in California. If I ride that area on a weekend I start further up the mountains like, Strawberry/Josephine, Chilao/Charlton, or Waterman.
Chantry Flats area is a good weekend ride, as the paved road is probably still closed so not many people out there. Winter Creek/Mt. Zion/Gabrileno is great loop. But you will have a possible mile hike-a-bike up the Sturtevant Trail to Mt. Zion.
On the weekends many downhillers start at Eaton Saddle and come down Upper Sam Merrill, Middle Sam Merrill, Sunset Ridge, El Prieto. Just a warning not to go up those trials, not that you would want to…they are very exposed, steep, rocky and tight in places. Not a place you want to send a downhiller off the trail.
My point is: weekday rides out there are much better.
If you have not explored Mt. Wilson and the San Gabriel’s get out there you are missing allot!