Las Vegas visitors rose in March more than in any other month in its history, thanks to college basketball tournaments, car races and conventions. The Las Vegas Convention and Visitors Authority reported that 3.7 million people came to town last month, up 4.3 percent from March 2013. Tourism officials say convention attendance was up 21 percent, mainly because the CONEXPO-CON/AGG construction convention. The event happens every three years and drew nearly 130,000 people. Room rates shot up for the month of March. The average daily rate hit $134, up 21 percent from the same time a year ago. Gambling revenues…