How often should you water Yucca in a pot outside?
People often ask this kind of question, but it's a question that has no real answer. The question you're really asking is "how do I know when to water my yucca?" After that, the question is "how do I know how much to water it?" I'll try to answer both questions.
The simple answer to "how often" is "whenever the plant needs it." And when does the plant need it? In the case of the yucca, it's "when the soil in the bottom of the pot is almost dry." The only way to know if it's time to water is to test the soil moisture. You can do this in several ways: https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/testing-moisture-in-plants.htm
On a moisture meter, it will show around 1/4 of the way between dry and moist. I'll emphasize the 'in the bottom of the pot' part - often, testing the soil moisture at the top of the soil is insufficient, because the soil underneath can easily stay wet while the top dries out.
After your yucca has reached this level of soil moisture, or aeration, how much do you water? Simple. Make sure that the soil is tucked up tight to the sides of the pot, then water till you see a run-off from the drainage holes. You don't have to drain it if it's less than 1/4". That's all there is to it. You probably won't have to water again for 1 week, maybe even 2 weeks if the light is low.
FYI, here's an article on yucca: https://www.gardeningknowhow.com/ornamental/foliage/yucca/growing-yucca-indoors.htm