I've been doing a lot of research into cacti fruit species recently, and S. queretaroensis is definitely up there. Thanks for the extra datapoint on its flavour. This definitely seems to be a well-appreciated cactus species. Productivity commonly peaks 20t/ha, which for comparison is better than all annonas I've seen except atemoya, and triple that of mangosteen (although still a far cry from common "garden" staples like tomatoes, cucumbers, etc, which are dozens of t/ha in the field and hundreds in the greenhouse). The fact that S. queretaroensis achieves this areas of low rainfall / low fertility makes that impressive; there's not many crops that will grow there without significant help**, and I bet that you could get even higher rates with irrigation and fertilizer. The main downside is that it doesn't produce at those levels until 40 years of age. Production supposedly steadily ramps up to 16t/ha in the first 20 years (yields are considered commercially viable after 10), then slows down its increase, and after 40 years starts its decline (but 100 year-old plants can still produce). Given the poor growing conditions they're usually grown in, I'd imagine that proper irrigation and fertilizer application could speed this up somewhat. That said "some" fruiting can start as soon as the first year of planting cuttings that had been previously fruiting from an existing plant. Planting a stenocereus is an investment in the future.
** There are, of course, higher yielding cacti out there. Opuntias for example can be up to 50t/ha with irrigation and fertilizer! But while they taste good, they also have despised glochids, and the seeds are a pain. Dragonfruit obviously is also a good producer (~50t/ha) when it receives proper irrigation and nutrition. But as far as cactus grown in desert environments go, and particularly as far as columnars go, S. queretaroensis isn't bad at all. Just slow to reach full production.
Note that the area they're used to doesn't get frosts very often, and never gets hard frosts. Also, while they average 700mm a year (27"), it's mostly in the summer, not the winter like SoCal. They can still grow with less water than that and are considered very drought tolerant. So someone in SoCal could give them summer irrigation when water supplies aren't restricted, but they wouldn't die in years where there's a watering ban.