What can I say here. I've helped at a shop for free after going to school to learn a bit but wouldn't recommend it. My concern here would be you could be learning to do things the wrong way and not know why. If you went to school first your foundation would be good then your experience will follow. Ever try to change a bad habit? Don't get me wrong there are some excellent self taught welders out there. I'm sure I'll hear too.
I admire your drive to get into the field. I followed a steel truck one time to find a fabrication shop. The owner laughed when I told him what I did, but, I got the job. Keep looking, there has got to be a shop that needs a helper, who doesn't mind grinding and fitting.
Forgive the rambling here and good luck!