I spotted the first truck in Sebastopol yesterday but didn't have time to stop. In Richmond today on MacDonald and 37th there was a truck selling cherries at 2 lbs for $5 or $3 for 1 lb.
As is often the case for these roadside trucks, the cherries are probably from the Fresno area. As is also the case, the are almost all doubles (conjoined cherries)
However, they were pretty good ... crisp, juicy and slightly tart. I'm guessing maybe Bings but that seems too early.