The area's home prices have a 60-percent chance of dropping, one of many factors making San Diego the riskiest real estate market in the nation, according to a quarterly report put out by a California mortgage insurer.The report, put out by the Bay Area insurance company PMI Group, is well-respected by experts, who said it usually gives an accurate picture of the state of the nation's 50 largest home-buying markets. However, they stressed that the report is merely the latest in a long line of analyses that point to something the industry already knows: The nation's housing market is cooling,...