TIJUANA, Mexico — Residents in the Canon de la Pedrera neighborhood of Tijuana about six miles south of the border are complaining about a putrid odor that is so strong some days it has made a few neighbors feel ill. “Yes, it smells horrible all the time — sometimes it’s stronger and other times less, but it always smells,” said Daniel Ruelas, the president of the Comite de Vecinos, or neighbors’ committee. The smell has lasted for weeks and seems to be coming from a nearby concrete channel where some residents appear to have built their own makeshift drainage system to dump their waste water …