(a) In a county with a population of 3.3 million or more, the commissioners court of the county may:
(1) prohibit off-premise portable signs in the unincorporated area of the county; or
(2) regulate the location, height, size, and anchoring of, or any other matter relating to the use of, off-premise portable signs in the unincorporated area.
(b) A regulation imposed by or adopted under this chapter does not apply to an off-premise portable sign in the unincorporated area of a county with a population of 3.3 million or more.