Caldera Forms and Smart Groups
Jsgoti, Welcome to CiviCRM SE. You definitely achieve this using Caldera module. All you have to do is 

1 - Create a form with First Name, Last Name and Email field and also drop down in Caldera form.

2 - Click on Processor tab. 

3 - Add a new processor of type 'CiviCRM Group'.




Then configure the settings to link contact to group

Add condition by clicking condition tab to add to group based on selection.



HTH

Pradeep