L.A. County home sales fell 25 percent in July, the eighth straight month of declines, according to a survey by DataQuick Information Systems. The median price of all L.A. houses and condominiums closing escrow was $520,000, just a shade above the $517,000 in the previous month and up 6.6 percent from a year ago. DataQuick has San Diego's median price falling 1.8 percent to $487,000 last month from a year earlier. The numbers are slightly different than the ones reported earlier this week by HomeData Corp., but the directions and percentage changes are pretty consistent. Yet another set of July housing numbers, this one from the California Association of Realtors, is due out later this month.