If you have to download it then I'm confused what you mean by a cloud IDE. If you just mean a local IDE that connects to the cloud, then where does the cloud come in? Do you just mean an editor that works on remote files? If you mean an IDE that lives IN the cloud, then no you cannot run it offline as it inherently requires an online connection at some point.
Cloud servers and local servers can be very different. Not everyone hosts in the cloud and not every cloud is capable of reproducing local server hardware. If you're talking about colocation instead of the cloud then that's something different than the cloud. The cloud typically refers to someone else's hardware.
It is technically possible to partition OSX in a VM or on a PC, but it is against Apple's TOS and technically illegal.
I prefer to run my development environment in a VM so I can take it with me, regardless of internet access.