Can I call drupal_goto in form #submit handler?
Can you call drupal_goto in a submit handler: Yes
Should you call drupal_goto in a submit handler: No

Why?

The reason is that potentially other submit handlers might need to be called in order for things to work properly. If you call drupal_goto you would stop the execution flow and make it impossible for the other submit handlers to do their thing.

What you should do instead is to use $form_state['redirect'], which when set will be the url that is redirected to when the submission process is completed.

In your specific use case, however it could work since you don't want the node to be saved, but stopping the process in this way could give you strange bugs/side effects.

But you really should't be doing it this way.

Instead you should attach a validate handler to the node form. If the validation fails the node is not saved and you can display any message to the user via drupal_set_messsage or form_set_error. You could save in $form_state that the message has been displayed to the user and allow him to save the node anyway if he resubmits the form. This is what the validate handlers are built for, after all.