Thanks everyone.
kuhio98, that was some great info, thanks!

I found out that she leaves her dogs out while she's gone at work during the day. Honestly, dogs barking don't normally ever bother me.. but when it affects my dogs behaviour, it does get to me.

The problem with the tarp is that our backyard is a bit higher than theirs, and their dogs are usually on a high deck, so they can see OVER the fence, and are high enough that my dogs can see them.

Mickey is SUCH a freak (I mean that in a nice way!), he hasn't gone #2 since Monday now because of this... the only place he does it is the backyard. Grrr...

When I see the owner, I'll ask her if she knows how much her dogs back when she's away.. before I go crazy, lol.