Is there a way to tell the callout to use a DropDownList for the Location instead of a Textbox?

Alternatively, it would be acceptable to hide the Location field altogether, if I can add my own custom field and make it a DropDownList.

Joe, I have also requested this feature.  I hope they are working on it. 

Hi Joe,

Actually you can change the TextBox for field Location with DropDownList or event you can add your custom field in WebScheduler. We have provided a sample which you can find in WebScheduler sample project. The sample named EventOrganizer.aspx.
In that sample there are two additional fields which are : Notes, and TotalAttendees which added in EditingForm_Extended.aspx (Custom Editing Form)

About George's request, he asked more advance feature in WebScheduler which can allow user to view all events based on its Location, meanwhile for now we can only group it by the Resources. And we are still investigating the possibility to be implemented in WebScheduler. So Thanks for George for the valuable feedback.

Best Regards,

Dicky