Depends where you are.
If you stop by a Texaco, there's a good chance it'll be decently clean. QuikTrip (Aka QT) has some of the cleanest restrooms I've seen outside of a La Jolla office building I once frequented that came complete with a bidet and imported Italian marble draped everywhere.
Now to get the thread back on-topic I will mention that much progress has been made in space regarding evacuating waste. Similar technology would be needed on Everest if one didn't want to see the peaks and valleys turn from frozen white to frozen yellow-brown.
Personally, Everest has very limited appeal. I'd much sooner see undersea hotels - they'd be far more comfortable and more varied, scenic & interesting lodgings.
;-)