Since spring training stats for the players isn't that great of an indicator for the upcoming season's performance, one can only hope that is also true of attendance figures.
Average attendance for the 15 games the Marlins hosted at Roger Dean Stadium this spring was 3,950, the second-lowest home average in the majors. Only the Washington Nationals (3,886) had a lower home average
I'm pretty sure the Nationals will draw well in their new stadium, that is suppose to open this year. The Marlins, however, may be another story.