If I have a login screen on a non-ssl page and when they submit the form it goes to a secure page, is it transmitted securely?
Yes, the SSL connection is created before the data is sent.
But for the peace of the mind of the users (who probably wouldn’t know that) i would recommend making the login page secure too.
Anyone on the non-SSL page will not know that there is any security involved unless that page also uses SSL. They will have no way of checking the security certificate to ensure that once they login they will actually be on your site and not some lookalike site that is stealing their password.