Going through the attribute list for
apex:inputField, I don't see anything that looks like it'll help.
Here's what I suggest: (if using Chrome) right-click and select Inspect Element over the User-type picklist, and see if there's a specific class attached to that element. Then using jQuery, in your
.ready function, hide all elements of that class. Hopefully, the class name for user-type picklists is unique, so it won't bother any other part of the page.
Example: If the class name for user-type picklists = "
userType", have the following jQuery
var j$ = jQuery.noConflict();