Las Vegas homebuilders struggled during the first two months of 2011 and aren’t showing much optimism for a quick recovery in the market. Sales of new homes fell 19 percent in January and February compared to 2010, while sales of existing homes rose 1 percent as prices continued to fall, according to a report released Monday by SalesTraq. Buyers closed on 502 homes in January and February, down from 621 in the first two months of 2010.