Rancho San Gregorio's terrain was dramatically different from the valley-floor grants that characterized the Santa Clara Valley. The rancho occupied the western, ocean-facing slopes of the Santa Cruz Mountains, where the marine influence creates a cooler, wetter climate than the sheltered valley to the east. Redwood forests covered the canyons, while grasslands and coastal scrub dominated the ridgetops and marine terraces. San Gregorio Creek, which gave the rancho its name, cut through the mountains to reach the Pacific at the small beach community that still bears the name.

The coastal ranchos of San Mateo County developed differently from their inland counterparts. The difficult terrain, cooler climate, and distance from major settlements kept population sparse. When American acquisition disrupted the rancho system, the coastal properties were slower to develop, preserving their rural character longer than the valley-floor grants. This accident of geography and economics means that the San Gregorio area retains an agricultural and open-space character that the inland ranchos lost decades ago.

Today, portions of Rancho San Gregorio's territory are protected by the Midpeninsula Regional Open Space District, including the La Honda Creek Open Space Preserve. The town of San Gregorio remains a tiny coastal community. The farmland around it continues to produce crops and support cattle ranching, activities that would be recognizable to Antonio Buelna if he could return to his grant. In a region where most former ranchos have been paved over, Rancho San Gregorio's coastal remoteness has preserved a landscape that still resembles, at least in outline, the land grant that created it.