Well, since you're planning on getting the wireless ones, that certainly gives you more options.
Under the eaves is good because of the protection from the elements and a convenient install. HOWEVER, I think pointing the speakers at your neighbors could be problematic.
I just finished installing my (brand X) outdoor speakers and mounted them close to the listeners but pointed at our house. I am convinced that was a good strategy. Music is as loud as I want it to be but a non-issue for the neighbors.
In your case, I'm not sure I'd go all the way to the back fence (need pictures!). If there is a way to keep them on the deck but pointed at the house, that's what I'd do. Especially if you get the wireless ones, you could bring them in out of the elements when not in use.
Wasn't there discussion of a solar panel on the wireless ones to help recharge, or did I dream that? If there is such a feature, you probably wouldn't want them under the eaves anyway.
