On a fall Saturday, a little before her 60th birthday, Allison Blanks got a letter. It had four typed sentences. She read them in her El Cajon apartment, which she moved into almost two years ago after a long stretch living out of motels and a Chevrolet Spark. “The Housing Authority of the County of San Diego has made a decision to terminate your participation in the Local Rental Subsidy Program,” the letter said. Starting February, “You will no longer receive benefits and will be responsible for paying the entire rent.” The news wasn’t entirely a shock. Blanks remembered being told that the a…