Something that stinks to deter my neighbours from sitting at the front of my house?

Basically, the tenants from the flats to the right, meet up with people from the flats to the left. And as my house has the only low wall in the street, they sit there all day. And have done now for the last 5 months. I have a hedge up my path I could secrete something inside of that they'd never find, but I'm thinking of partly burying something... I just need to know what. Like, yeah I could go and ask them to move, but they're unlikely to take kindly to that and I'd be worried they'd cause damage while I'm out at work. Also... They're there from 10am until 8pm almost every day. They drink cans and are all fit enough to work, but none of them do. What do they talk about? And do they not get bored? Any suggestions for a stinky solution?