I tried a makeshift version of this some years back by using some clay flowerpots ( I plugged the holes at the bottom) buried in my raised beds. I covered the tops with old tiles. The tomato plants did very well. It looks as if I shall have to try this again this year.  Those ollas look very attractive but I have never seen them here in the UK....I did see them in Mexico when I was visiting friends years ago.

I think mulching is so important in dry summers, use whatever you can, laying it on as thickly as you can. Above all don't let your chickens get anywhere near it.....they are mad about mulch & kick it around with gay abandon........