If you go to Options | Settings in CCleaner Portable you can still enable Inform me of updates to CCleaner, but if you are using the portable version then you are likely only plugging in your USB drive and running CCleaner Portable off your thumb drive when you want to run the occasional disk cleanup.
Sadly, I just unzipped the CCleaner Portablev on a USB thumb drive and I'm seeing the same obtrusive pop-up ads in my system tray.
