The best beginner training for PR, aside from a degree in journalism or communications, is to join an agency. Agencies are usually open to hiring inexperienced employees for their entry-level positions. From there, you participate in hands-on account work that provides good training in creating basic PR documents and frontline experience in media relations. Many corporations hiring experienced PR pros consider agency experience critical. Once you have a few years of agency time on your resume, your career options open up in many different directions.
The worst background for PR, in my opinion, is sales. The tactics used do not translate at all (but sales people seem to think they do).