I do appreciate you sharing your experience, even if I don't have a lot of insight about that particular species.
The trailing/mat forming ice plants that we have here (about 6 or 7 different species that I have not all identified, none of which match yours) are all drought tolerant in our coastal climate, which is similar to yours but cooler and drier (10"/year, 70% from Dec-Mar).
They will survive with zero supplemental water here when established, though it is important to provide regular water during their first dry season in the ground. Plants growing in difficult places (rocky/sandy soil that doesn't retain much water) will tend to be dwarfed and they may turn brown by late summer, but do come back when it rains in the fall and winter. So I guess if you're going for a nice green appearance, you might have to water some. I can't imagine watering more than every 2 weeks even in the peak of summer, but our temps are way cooler than yours (average high temp in August was 75°F).
Also the growth will be quite different in sun vs. shade. I don't think the average trailing ice plant has any particular demanding needs about light. They all do fine in full sun here, but I've also seen them in shady places. The stems will grow longer and weaker, as will the leaves, in lower light. Given a sufficient period of neglect, the ice plants in the public garden would probably take over everything, sun or shade, as they can penetrate pretty far in the undergrowth of other plants (though with longer, weaker stems).
I have never seen a trailing/mat forming ice plant that actually works for foot traffic. They all tend to get crushed pretty easily. Though the older stems are harder and withstand more pressure, so where foot traffic passes through a patch of ice plants, the brown stems are basically all that's left. It doesn't mean the end of the plant (collateral circulation, redundant stems) but it isn't pretty. Basically there is a foot path or foot prints where people pass through regularly.
