Thank you for your help!
The neighbors have an advantage over me when it comes to using a camera. They're interested in focusing in on my kitchen window which I leave the curtains open in order to bring in sunlight. In my case, I'd have to have cameras positioned to cover not only my front and backyard, but also theirs, and also the area between the houses. Keeping the cameras hidden would make it more difficult. I'm not sure how I'd even be able to hide them if they're to watch over a wide area.
As for my reason for contacting their landlord, I guess I was hoping he would be bothered enough that he has tenants causing problems for their neighbors that he would either convince them to straighten up or move out, or even evict them. I doubt landlords like tenants that attract police. I remember when I was renting a small house and the homeowners next door complained about me to my landlord. The landlord listened to them. (And then I discovered much later that they had retained a key from a former tenant and were entering my house and stealing stuff while I was away). But anyway, I was thinking of just calling their landlord. Would that work? Or should everything be in writing?

