This does work for me, even with WordPress’ built in search. Just adding the onSubmit attribute solved the issue for me, searching for AT&T now brings up the results that it should.
When writing ampersands in WordPress’ post title box I still have to add the “amp;” otherwise my pages don’t validate. WordPress should really deal with that for me.
And, after hitting enter to submit the search form “AT&T” turns into “AT& amp;T” (no spaces) before the page reloads. This isn’t a perfect solution, because a perfect solution would be for WordPress to deal with this natively. But, at least it works now.
@mrtemple Thanks for all your hard work, I’ve been searching for a solution to this problem for a couple of months now and haven’t even found any discussion of it. I’ve found the same problem on other WordPress sites and it’s almost as if no one knows that the problem exists.