You can setup an action (same as the border) if you want to use the same font in the same position everytime.
I have not done this yet but I beleive others have and it works well.
Basically you then would just need to run simple borders action and then Signature action and your done.
here is a qoute from MattK from another thread explaining how to setup an action.
Matt. K wrote:OK! Let's set up an action! Open 1 image. Go to actions/new action. Give the action a useful name...ie, save for web. Click the record button at the bottm of the Action menu. Go to IMAGE/IMAGE SIZE and alter the size and resolution to your requirements/ go to file/save...and save the image in a new folder that you have created for holding the resized images. Stop recording by hitting the appropriate button bottom of the Action menu.
Now go to FILE/AUTOMATE/BATCH...select your action and select the appropriate folders. Set up a trial with 2 or 3 images just to make sure it works before you commit the action to your folder of 500.
Hope this helps. Let me know if you hit any snags and I'll try and get you over them.