Home sales in the Conejo Valley, including Thousand Oaks and Newbury Park, turned downward in July. The Conejo Valley Assn. of Realtors reports the sale of 222 single-family houses during the month, compared with 293 in June and 232 a year ago. Last month’s median price was $268,000, down from $288,000 in July, 1993. . . . Rexon Inc., a software producer with a plant in Simi Valley, received a $25-million credit line from Sanwa Business Credit. . . . Ventura County’s jobless rate climbed to 9.3% in July from 7.3% in June. Officials blame the rise on seasonal layoffs on farms and in schools. . . . Talbot Design Group, a Westlake Village advertising agency, has launched a campaign observing the 60th anniversary of Los Angeles’ Farmers Market. In addition to the historic market, Talbot’s accounts include The Oaks mall and GTE California’s Visnet division. . . . The Oxnard Minority Business Development Center opened an office in that city’s Heritage Square. The center will hold an open house from 4 to 7 p.m. Wednesday at its new location, 741 S. A St.