Joe, yuccas are one of my favorite plants. They are very hot and cold hardy. On watering schedule, desert plants actually love to be water regularly. I water my Joshua yucca every other week to keep it looking happy. On trimming , you can trim off the old and deaf leaves or leave it natural. Personally , I left all my yuccas "natural". However, I have seen them in fully trimmed and it look great too. Happy gardening. Nick.

The cactus and agave will do fine with no supplemental watering. At the most, only about once a month if we get no rain. Overwatering them will kill them, underwatering is not likely to.

What kind of barrel cactus? What kind of Agave -- A. americana? What kind of Yucca?

Most Agaves will benefit from regular water, at least every two weeks through most of the year (less in winter) and as often as twice per week through summer. They can survive with less, but will look and grow best while well-watered. Many non-native cacti also do best with regular water through much of the year, but do not want water while dormant in winter. Native cacti need very little if any supplemental watering. It is important to let succulents dry thoroughly between waterings.

I water nearly all of my agaves every other week spring/summer and early autumn, and then only once a month in winter IF we've had no rain. I water established native barrel cacti once a month in late spring, summer and early autumn, and not at all mid-autumn until late spring. Like others said it's important to make sure the cacti get DRY between soakings. Golden barrel cacti appreciate water every other week, but native ones can definitely go longer once established. Let us know what you do and how it works out! Happy gardening!