I have scoured the web for tutorials for adding custom signup attributes in Magento. While there are a few solid tutorials out there, my favorite being this one: custom customer
I am very happy to say that I have been able to find a solution to my problem! After posting on the Magento forum and not getting a response I decided to dive in and solve this for myself. I am hoping that my solution will help other Magento dev's that might be experiencing a similar problem.
1. I found the following tutorial which was incredibly helpful: http://www.magentocommerce.com/wiki/5_-_modules_and_development/customers_and_accounts/registration_fields
2. Unfortunately my theme did not have the register.phtml file located in: app/design/frontend/default/yourtheme/template/customer/form/
3. After reading a few other Stack Exchange and forum posts I found that in this case Magneto default's to the base located in: app/design/frontend/base with the register.phtml file located at /app/design/frontend/base/default/template/customer/form/register.phtml
4. Here's the catch that some of you also might be running into. After thinking I had figured it out, I made changes to this file and...nothing, no update on the frontend. I tried flushing the caches but it didn't work.
5. So I kept searching and found that in my case (and potentially in yours!) the register.phtml is actually stored under /app/design/frontend/base/default/template/persistent/customer/form/
6. After editing that register.phtml file I was in business
I hope this helps those of you who are running into this same issue. Feel free to update this thread if you have any questions, happy to help in any way that I can.