ssh-port.diff

# Enable ssh_port option in vagrant-digitalocean
# Diff of /lib/vagrant-digitalocean/actions/create.rb

           # wait for ssh to be ready
           switch_user = @machine.provider_config.setup?
           user = @machine.config.ssh.username
+          port = @machine.config.ssh.port
           @machine.config.ssh.username = 'root' if switch_user
+          @machine.config.ssh.port = '22' if port
 
           retryable(:tries => 120, :sleep => 10) do
             next if env[:interrupted]
             raise 'not ready' if !@machine.communicate.ready?
           end
 
+          @machine.communicate.execute("sed -i 's/Port 22/Port #{port}/' /etc/ssh/sshd_config && service ssh restart") if port
           @machine.config.ssh.username = user
+          @machine.config.ssh.port = port if port
 
           @app.call(env)
         end

For Ubuntu on Digital Ocean:

This is a diff of the vagrant-digitalocean plugin's create.rb file (as of Aug 7, 2014). It appears that the DO plugin must initiate the DO droplet using ssh port 22. These edits temporarily set the ssh port to 22 for droplet creation, then back to the port specified in the user's Vagrantfile.

Without these changes, if the user has set a non-default port for config.ssh.port in the Vagrantfile, the vagrant up droplet creation hangs forever due to the DO plugin's inability to connect via ssh.

I'd love a more universal solution anyone may share.