Sales of existing homes in South Florida rose in June, according to the Florida Association of Realtors. Home resales in Broward County went up 35 percent from a year ago, while Palm Beach County resales rose 15 percent. But home prices in both counties dropped, to $204,800 in Broward County in June from $305,400 a year ago, and to $250,300 in Palm Beach County from $334,300 a year ago. The June average sale prices are slightly higher than May’s averages. Local brokers said the $8,000 first-time homebuyer tax credit is leading more people to jump into the market. But Lawrence Yun, chief economist for the National Association of Realtors, blamed poor appraisals for preventing more deals.