I had the same issue at Baton Rouge. Walked to the gas station and they had what looked to be a permanent OUT OF ORDER sign on the bathroom and wouldn't budge when I protested. There was also enough security activity in the parking lot to prevent me from peeing in the bushes, so pretty much the worst of both worlds.Only having to cross the street to use Gas Station restroom is nothing. Try the Baton Rouge Supercharger in the wee hours of a weekend (twice for us now). Everything closed. Finally found a Motel a few blocks away that allowed us to use their restroom. On our 52 hour I-10 west trek from Saturday noon Jacksonville Supercharger to Monday afternoon arrival home in San Diego I made sure to bring a plastic container that I could use, then empty in the bushes. Worked great when no restrooms are available at the Supercharger. Unfortunately my wife had to wait until we could drive somewhere for her to use.
Buttonwillow is fine at night. You're alone but nothing else is going on there. I'm a night owl and have stopped in there quite a few times late at night even in my ICE days.