Leaving the Palomar Observatory, we plunged through the twists and turns of East Grade Road (S-7) to California 76 (more twists and turns) to California 79 (few straight sections). San Diego County Highway S-2 (gnarled and sinewy) leads to the dirt of Blair Valley Road. Blair Valley Road winds along, and offers travelers side trips to Indian/Native American pictographs and mortreros (meal grinding sites). Bypassing the Pictograph and Mortreros road will lead to the trail head parking area for the Marshal South trail. Carry plenty of water; there's none to be found along the trail. By the same token, the trail is steep and rocky, and the sunlight harsh and unforgiving. Be prepared with sunglasses and sunscreen. Winter temperatures are much more temperate, sometimes dipping below freezing, but the trail still requires preparedness.