Thank you!

I'm not sure if it really is the best time, but because all my plants are in black plastic pots and they get very hot in the sun, I thought I'd see if it worked. And it did! At the nursery where many of these plants have come from. they water with sprinklers twice a day -- for 15 mins at about 10 am and another 15 mins at 2 pm.

We're moving into the wet season now, so I expect to have to water them less frequently. (Fingers crossed for some decent rain this summer!)