Since their first game in 1993, the Marlins have played at Dolphin Stadium, where their lease expires after the 2010 season. The Miami Dolphins and Miami Hurricanes play football there, and Samson said the Marlins have talked with representatives of both teams about remaining in the stadium in 2011. "We're confident we can get an agreement to extend the lease one year," he said. Opening date of Florida Marlins new ballpark delayed until 2012 - MLB - SI.com
I dont see the problem in this even tho people are going to go nuts about the field when football season starts.
Just occupy a local high school baseball field for the time being. There should be enough seating capacity.