It does best in climates far colder than yours -- Sunset zones 1-17, 14-19. (Your zone is likely 23 or 24.)

Paraphrasing from Sunset Western Garden Book: Aspen is native to elevations of 9,000 ft and performs poorly or grows slowly in lowlands. Usually short-lived in warmer climates.

I suggest you get your aspen-fix by taking periodic trips to those places where the trees are in their glory.

You could try a close relative, cottonwood. Not saying it's a great tree but if you gotta have a poplar.
I'm growing a quaking aspen out of range here in GA and I'm not impressed.

Trembling aspen is native to these parts and makes up the vast majority of the deciduous forest, and is not considered a desirable species. Sure, it has charm in it's white bark, dainty foliage and bright yellow autumn coloring, but other than that I would not recommend it for residential planting. It also prefers "cooler" climates and can sucker badly!

Terry