I should do some more research so that I can use the right terminology to answer this question, but basically no, you can't use SSH keys to login to a virtual terminal/console. Further, for some, "the long way" as you describe it, is actually much easier than using the remote console provided in OpenStack Horizon (which is what I assume you are using). In fact I have a small OpenStack cluster and Horizon isn't even installed. :)

Keep in mind that SSH (private) keys are not stored in OpenStack database at all for obvious security reasons. They are for your use only. And there is no need and no way to use an SSH key through a website - after all, it's easier to type in a password than a typically 4K key.

What you can do to access the instance easily with the use of a password, is to set it using the "post-installation customization script" (last tab on the Launch new instance window).

Put in a script like that:

#!/bin/bash
echo "root:password" | chpasswd

Then just log in with the username "root" and password "password". Keep in mind that if for any reason instance does not discover networking (i.e. if your DHCP agent is down) and doesn't pull "EC2 metadata", these credentials will not become valid.