I never thought I'd say this but I agree with HBCU 100% (I know,

, right?)
We were discussing a similar topic in one of my Black studies classes awhile back. Personally, I'm against blackface "art," regardless of the race of the owner. I feel that it brings us back to a time in history when Blacks were made mockeries of; people to be laughed at, considered foolish, and treated as ignorant individuals.
Some Blacks, however, do not feel this way, such as the previous owner of the home. Still, as HBCU stated, I think it would be in your best interest to remove the piece from your yard. Otherwise, people will perceive you as a racist. Your classmates, your professors, and your neighbors will all label you and treat you as something that your may not be. Word gets around. What if you intend to work in the area in which you live, and employers stigmatize you because of that piece? Is it really, really worth it?
I suggest that you speak to the woman who owns this art. Tell her exactly what you explained to us. Tell her how uncomfortable you are with having the piece in your yard, and what implications it can possibly have on your life. Obviously, the woman is clueless if she thinks that it's okay for a white man to have a Blackface piece displayed in his front yard. She should completely understand if she has any sense whatsoever. If not, defintely, defintely hide it or put it in storage.