A new America’s Favorite Cities survey by Travel + Leisure readers ranked San Francisco among the dirtiest cities in the nation. San Francisco came in at #12 out of 20.  But hey, the good news is that at least we ranked better than Los Angeles, which came in as the third dirtiest big city.

Our poor ranking is a double blow. Travel+Leisure readers are exactly the kind of customers we want to attract to our leading industry – tourism and conventions. And for a city that ranks in the top 10 for environmentally friendly cities we’ve apparently got some more cleaning to do.

Perhaps prompted by this news, Mayor Ed Lee announced he is bringing back the San Francisco Clean Streets program, a city effort that fell to the wayside a few years back. The Clean Streets program focuses on keeping commercial districts free of trash, graffiti, and general city grime. The program is slated to start on July 1.

What do you think? Why is San Francisco so dirty, and what should we do to improve? Log-in and weigh-in below.