[development] URL preparation

I'm hooking operations_apply and stringing together url parms to use with prepopulate. When I do the drupal_goto(), the part of the url, for example, that should be /node/create/application becomes node/create/application%3F, so that I end up at the content creation page instead of the page for the specific content type. Is there an api function for munging the url before I give it to drupal_goto, or should I just do it with php?