I've got an evening flight out, so I will have an onward AA boarding pass. I'm just spending the day. I figured in worst case scenario, I'd wait until 7:30 and be first in line for the Admiral's Club showers, but it would be less of a rush if I could shower in another lounge that was open earlier than 7:30. Plus I wouldn't have to sit around loungeless for an hour or more.

I'll look into the JL departures lounge. Thanks! If anyone actually has exact opening times, that would be fabulous -- though I'm not complaining, as you've given me very good leads already.

Arigato!