German cockroaches favor warm, humid spaces near food and water — kitchens, behind appliances, under sinks — and San Juan's a humid subtropical climate in the Hill Country transitioning to a warmer, semi-arid climate farther south toward the Rio Grande Valley keeps them active most of the year. American cockroaches, larger and reddish-brown, prefer basements, drains, and utility rooms. A blend of Hill Country stone construction and warmer-climate South Texas homes built for heat rather than cold.
Treatment starts with locating the harborage points — the tight, warm, food-adjacent spaces roaches actually live in — and applying gel bait directly there rather than spraying open floor space. This targets the colony at its source and avoids the resistance issues that plague over-the-counter sprays. We follow up to verify the population has collapsed, not just scattered.