Ask Mr. Smarty Plants

Jasminum sambac, Arabian Jasmine, is native to southwestern and southern Asia, and is hardy from USDA Hardiness Zones 9 to 11. This Floridata website has some information on it, as well as a warning about invasiveness:

"The Florida Exotic Pest Plant Council lists this species as a Category II exotic invasive. This indicates that it has increased in abundance or frequency but has not yet altered Florida plant communities to the extent shown by Category I species. These species may become ranked Category I, if ecological damage is demonstrated. Arabian jasmine cannot be recommended for landscape use in Florida and caution should be exercised when considering this plant for use in similar frostfree climates."

The Arabian Jasmine is hardy in Zones 9 to 11, and the Floridata website above has information on pruning and culture. 

While there is Malpighia glabra (wild crapemyrtle) which is native to South Texas, you very likely have Lagerstroemia indica, crape myrtle, native to temperate and tropical Asia. Because the Lady Bird Johnson Wildflower Center is dedicated to the growth, propagation and protection of plants native not only to North America but to the area in which the plant is being grown, we are not going to be able to help you very much.

We established that Las Vegas is in an area where the USDA Hardiness Zone can vary from Zones 8a to 9b. This article from Floridata will give you pruning, deadheading and culture information on Lagerstroemia indica, and we learned that it is hardy from Zones 7a to 9b, so it should be all right.