Regal, I don't know how long it's been since you've been in these parts, but developement (sadly) has pretty much chewed up nearly all of the foothill habitat. There is no habitat left around the old Marine Base anymore worth spending the time on. All the old farm land between El Toro and Tustin is now completely developed.
There is a toll road now that goes from Tustin/Orange all they through Mission Viejo, and an adjacent road from there to the Ortega Hwy. The area's surrounding this has been developed. It's just a matter of time before we see the area from Yorba Linda/Anahiem Hills to Corona become one land mass of homes too, it's nearly like that now.
Central and South OC has become extremely populated in the past ten years. I used to be able to stop in the middle of the roads and not worry about oncoming traffic. Now it's scary just to pull over on the side of the road, with the speeds everyone travels on them.
I've been in the OC for 16 years now. In that time I have seen field upon field, and hill upon hill get bulldozed and developed. Once they put the toll roads through the Santa Ana's and through the western foothills it's been teeming with developers. "If you build it, they will come."
With these new passageways came a volumn of cars that use them. Now every avenue that the toll roads have exits for has become inundated with heavy traffic. Santiago Canyon is one of them, being a major portal to Lake Forest and Mission Viejo. The other canyons in the area are also seeing more traffic as a result of this and the population explosion of mountain bikers puts a damper on hiking journeys.
Since the developement along the 15 Fwy from Corona through Lake Elsinore, and all the way to Temecula, all roads in the foothills of Orange/Riverside county against the Santa Ana's are being used with frequency. The Ortega Hwy that cuts through the Santa Ana's, is a prime example of a road that has become a major vein since the development along the 15 Fwy in Riverside County. I can't really speak for the southern part of the range, as I haven't been there in sometime but I can only guess it's the same.
By the way, Love them boa's.