Sales of existing South Florida homes are on the rise as prices keep dropping. August marked a second consecutive month of year-over-year sales increases, though experts say recovery isn’t due until late next year at the earliest. Broward County had 604 homes trade hands last month, up 12 percent from 538 a year ago, the Florida Association of Realtors said Wednesday. The median price there plummeted 27 percent, to $269,800 from $368,800. Sales in Palm Beach County increased 10 percent in August, to 623 from 568 a year ago. The median price fell 12 percent, to $323,300 from $366,200 last August. Despite the year-over-year decline, Palm Beach County’s median was up from $291,300 in July.