I would bet largely recreational use. See a lot of horses in Portola Valley and Woodside, and a few scattered in rural areas between San Jose and San Francisco,

I would bet largely recreational use. See a lot of horses in Portola Valley and Woodside, and a few scattered in rural areas between San Jose and San Francisco, though it tends to larger numbers on a few plots and a couple of ranches specializing in either equestrian training or long time horse housing, and one never sees a single horse on smaller plots, most people who have enough land for one horse will have multiple for companionship to each other. This was also true when I lived outside of Houston a few decades ago. Working horses are pretty rare except for carriages meant for tourists and law enforcement anywhere close to urban or suburban areas.