People entering Napa County through American Canyon might see a large tourist-orientated sign saying “Where Your Napa Valley Experience Begins” — with a Pacific, Gas & Electric substation as a backdrop. The sign depicts a vineyard and farmland, with mountains in the distance. Behind the sign and its bucolic depiction, though, is the tangle of metal structures and wires that make up the substation. Support local news coverage and the people who report it by subscribing to the Napa Valley Register. Special offer: Subscribe for $5.99 per mo… The American Canyon Planning Commission wants a more welcoming environment for the city’s welcome sign. On Thursday, it approved PG&E’s landscaping plan for…