I would say start with talking to them. just tell them it looks trashy and you would appreciate them cleaning it up or at least moving it out of sight.
Unless of course you think they might be the type of people to retaliate if you do end up getting the code enforcement out on them. In that case just stick with the calls to code enforcement. Keeping calling until they do something.
Unless of course you think they might be the type of people to retaliate if you do end up getting the code enforcement out on them. In that case just stick with the calls to code enforcement. Keeping calling until they do something.