check out the SpatialReference parameter in the search cursor. Unfortunately you cannot directly convert coordinates using gp.describe, so you would either have to:
1. Using the SpatialReference parameter in the search cursor, loop through all the features keeping track of the xMin, yMin, xMax, and yMax extents of each feature, and then compute the xMin, yMin, xMax, and yMax for the entire layer.
2. Using gp.describe, get the layers extent, construct a polygon feature for it, project it (using the project tool), and then reread the coordinates.
