I want to upload some files to the cloud and leave the there to see/use. I don't want them on my pc as they take up space (ie no syncing ) If I uncheck sync with local pc, it won't let me do anything to cloud folder. I am using Ubuntu One
If your pc is linked to Ubuntu 1 the files will keep in sync with your account, no way to change this (not on a per file / per folder base).
You could however unlink your pc and upload the files via U1 web interface. You can also use one the many free file hosters / sharers / cloud services around, this would allow you to continue using U1 from your pc.
Anyhow, assuming the files have a certain size (and you intend to use them) you will not have much fun with your cloud-exclusive copy. You are way better off if you keep the stuff local and try to free up some space elsewhere.