I understand and know first hand of your concerns.
I live down the street to a home in foreclosure and the yard was just a mess. I called the HOA, listing agent and Bank to try to get it cleaned up to no avail. Because everyone in the neighborhood was so tired of seeing this eyesore, my husband and some other neighbors spent the day cleaning up the landscape. It wasn't the best way to spend a Sunday, but it does look much better.