Douglas County saw a slight drop in its taxable sales during the month of April.Totaling $40.2 million, there was a half percent drop compared to April 2011. So far this year, the county is running 4.6 percent ahead of last year with 2,173 locations reporting.The county's largest category, food services and drinking places, brought in $8.72 million, dropping 3.9 percent. General merchandise stores were also down, 3.8 percent, at $5.97 million.Building materials and garden equipment was down 32 percent from $4.3 million to $2.9 million for the month. But food and beverage stores were up 4.9 percent to $2.77 million.Merchant …