Until last week, when the Maryland Jockey Club and its owners, MI Developments and Penn National Gaming, reached an agreement with the state’s horsemen, there was a veil of uncertainty whether there would be any live racing in Maryland in 2011. But Laurel Park will open its gates Saturday for a 49-day meet that runs through March 26, the start of a 146-day season divided into three meets at Laurel and Pimlico.