If your server only allows public key ssh, you may want to allow ssh via password.

We run across these servers from time to time, most frequently on Pantheon/Mercury sites, as password ssh authentication has been disabled by default. I could be wrong, but I think disabling of ssh password authentication is something done by Eric Hammond's AMI. If that assumption is correct, this information may be useful to you if you are using his AMI or a derivative of it.

To enable password authentication, ssh into your server as root using a private key.