Houston sprawls across more than 600 square miles, and that geography is exactly why yard signs still pull their weight here. Paid ads target a radius. A yard sign targets a street. When a homeowner in Spring Branch sees your sign in a neighbor's yard three doors down, that is a level of proof no ad impression buys — someone nearby already hired you, and the work is visible.
Contractors get the most out of this, and the ones who do it deliberately treat it as a campaign rather than an afterthought. A sign goes up at every active job, stays through completion, and comes down when the crew leaves. Roofing and restoration crews working a neighborhood after a storm see this compound fast, because the entire street has the same problem at the same time and every one of them drives past your sign.
At $3–$8 per sign in volume, the math is forgiving. One job won from a whole 50-sign run pays for the run several times over. The two things that actually determine whether it works: put the signs where your customers are rather than where traffic is heaviest, and ask every caller how they found you so you know whether to reorder.
One Houston-specific caution. Coroplast is a temporary outdoor material and the Gulf Coast is not gentle with it. Signs left standing month after month through summer UV and storm season will fade and warp. Wire H-stakes bend in saturated ground after heavy rain, which Houston gets in volume. Plan on rotating signs and treat them as a consumable, not a permanent install.