Good Day Down_under,
I see you are not getting much help so I will give it my best shot. Regarding the language barrier you have nothing to fear. You will find that English is truly an international language and that many in the tourist trade speak and understand your language. We have been traveling internationally for over 30 years (just returned from Budapest yesterday) and only are fluent in English. As to Venice to Barcelona by train, it is an option but you are looking at at least a 16 hour trip with a change of trains in Milan. If you can handle potential luggage weight restrictions you might want to also consider flying. Europe now has many discount airlines such as the new Vueling Air offering Venice to Barcelona airfares for about 110 Euros...and its only a 2 hour flight (there are other airline options). If time is no object than you might also want to consider driving the route which would afford you an great opportunity to visit some of Northern Italy (such as the Lake district) and Southern France. Its a great trip although you would have to drive on the "proper" side of the road (the right). As to Italian train service, you will find its generally reliable and on-time except for those days when they decide to have a strike (pretty rare). If you are determined to use the trains you should do some internet research on the fares and various Eurorail ticket options.