Production of hydrogen using vinegar and metal for experiments If
 I cannot, or do not want to use electrolysis of water to produce 
hydrogen, is it a viable alternative to react vinegar (ethanoic acid) 
and iron (or steel, or copper) to form iron(II) or copper acetate? (Assume steel wool or copper wires.)

If I tried to fill a balloon with the produced gas (assuming no leaks 
apart from balloon), would the hydrogen leak out of the balloon faster 
than it would be produced?
Acetic acid will probably react to slow. If you want to produce hydrogen in the litre scale I would suggest to use diluted hydrochloric acid and zinc flakes or iron. But be aware that it can be difficult to control the reaction. In a laboratory you could use a Kipp's apparatus for this.