Help!

I live in a duplex and have very annoying neighbors!!! Their unit is a 1 bedroom and I don't know exactly how many square feet it is but it is probably almost half the size of ours which is about 900 sqft, so basically; small. Technically there is supposed to be 1 woman, "R" living there.....but her boyfriend "J" lives with her (no big deal), her 20-something daughter "M" and her husband "A" and their son who I think is 2ish, all in a 1 bedroom apartment!!! Only "R" and "J" actually work, so we get to deal with the lazy freeloaders M and A all the live long day!! They fight constantly....a couple of times I have gone outside to see their son crying on the front step and covering his ears while they scream at eachother, I hate it!


But, the problem that I need help with is this; we share a front step area. So, being that they are home all the freaking time and they live in a minuscule apartment; they are constantly on the front step....the entire front step!!! There are toys strewn everywhere (usually directly in front of our door so we have to kick them out of the way!), chairs, leftover McDonald's bags with old fries falling out, bikes covering the whole walk way! Plus they smoke, so we often have to walk out our front door into a cloud of smoke which I personally find repulsive! So......I am trying to find a way to partition off the front porch-ish area so that it

(a) will be more difficult for their toys and crap to be in front of our door - meaning it has to be something fairly sturdy.

(b) will ward off some of the smoke - something to block the terrible stink

(c) will keep me from having to see their constant mess every time I walk out my door - not see through!

(d) will get the hint through to them that half of this area is ours, god damn it!!!

We have asked M and A multiple times to keep the stuff on their side, giving the excuses that our dog is going to eat a toy which will cost us thousands of dollars to fix or that we are going to trip over something and break a leg which will also cost thousands of dollars since we don't have insurance! Needless to say, talking to them doesn't work, so I am taking the route of blocking the area so I don't even have to see them!!

Any ideas for something simple, effective and cheap! Oh, it has to be not too tempting looking or they will steal it (I told you, awesome neighbors!)
Here are some pics for inspiration:


Our door is the one on the far right side that you cant really see. I swear they cleaned up all of the stuff right before I went to take a picture! Oh and the hanging yellow thing is this stupid dollar store windmill that they keep putting up on our side even though we take it down every time! And the dirty ugly rug is theirs, also not sure why it is on our side, but I would never put my own out there because their kid would spill something on it or throw it in the dirt or something :(







And this is a picture of the lovely view out of my door, again cleaned up considerably! And yes, that is a smokers post which is disgusting enough as it is, but they don't even use it, oh no, they prefer to toss their butts all over the grass an on the porch!