Southern California posted the best July sales volume in three years and the fastest pace of any month since December 2006. But as volume saw double-digit increases in all but one of the six Southern California counties, median prices saw double-digit declines from 2008 levels in the same number of counties. A total of 24,104 new and resale houses and condos closed escrow in San Diego, Orange, Los Angeles, Ventura, Riverside and San Bernardino counties in July, MDA DataQuick reported, an increase of 18.6% from July 2008. Sales volume increased for the 13th straight month, driven by low mortgage rates, the availability of both Federal Housing Administration financing for first-time home buyers and improved financing for jumbo loans, a strong investor demand, and increased affordability, DataQuick said. But median prices in the six-county area were down 23% on average. San Bernardino County saw the greatest increase in sales volume (40.8%), but the July 2009 median price was down 39.1% from July 2008. In Ventura County, where sales volume decreased 3.8%, the median price was only 10.7% lower than 2008. The average monthly mortgage payment for Southern California buyers was $1,180, down from $1,193 in June 2009 and $1,710 in July 2008. Foreclosures made up 43.4% of house and condo sales in July 2009, down from 45.3% in June 2009 and the peak of 56.7% in February 2009. It’s the lowest percentage since June 2008. Write to Austin Kilgore.