If you put up a camera and see someone on it, how does that change anything?
You already know that someone has been in the yard.
By the time you see it, call the cops, get them there, the perp will be long gone.
Even if the cops see it and know who it is, they'll just tell them not to do it again.
No real crime as such, is being committed.
Getting rid of the drug dealer might be a better option.