Laundrymat seems to be the most common spelling for what I would call a laundromat. There is a Laundryrama in the Vieux Carre. I would call this a laundr-o-rama. I've seen a laundryteria too. Again, where I come from, when you combine laundry with an ending, we generally substitute an 'o' for the 'y'. Keeping the 'y' is a sign of ignorance or lazy sign painting. Live and learn. I haven't heard anyone say "laundromat" out loud since I've moved to New Orleans but therein may lie the explanation.
No sightings of an al-night automat yet. Now that would be the bee's knees.