Try this: http://stackoverflow.com/questions/23568345/how-to-hide-a-workflow-button-based-on-user-in-openerp-7

I had this same problem (and in my humble opinion, this should be a native option in OpenERP) and finaly I found the answer here:

help.openerp.com/question/11853/inverse-of-css-class-oe_edit_only

(I guess my karma isn't high enough to post a link to the answer, so i'll adapt it)

In my case, since I'm developing an entire new module, I created a CSS file with the following content (so, no need to edit base.css!)

.openerp .oe_form_editable .oe_view_mode_only, .openerp .oe_form_editable .oe_form_field:empty {
  display: none !important;
}

Don't forget to add it's declaration it in __openerp__.py:

'css': [ 'static/css/uc_css.css' ],

And to add the class to your workflow buttons

<button name="submit_request" class="oe_highlight oe_view_mode_only" string="Submit Request" type="workflow" states="draft"/>

And this way you can remove all extra (and confusing) buttons on form editing view, leaving only the "Save" or cancel options to the user