Is the customer always right?While it's a "tried-and-true" maxim of business that the customer is always right, it doesn't apply to egos. And that seems to be the problem you're running into. It's one thing to say, for example, that your steak is under-/over-done and send it back; it's quite another to tell the chef you want to come back to the kitchen and cook the steak yourself.
Your local restaurant owner might be willing to let you steam milk once -- maybe twice -- but she is clearly
not taking it in the way YOU mean it. It seems as though she thinks
not that you are trying to improve your HOME skills, so much as you're telling her that HER coffee is
$#!+ and you can do a much better job! You see what I mean? Ego.
Now given the quality between most restaurant-made espresso and even a "poor" café-made espresso, your local restaurant's espresso may indeed be $#!+ -- she may even know it, and doesn't like to be reminded!
Me? I've given up ordering espresso after lunch or dinner in 95+ percent of the restaurants I go to . . . I've had much better luck at independent cafés who -- in some cases without me even asking specifically -- have offered to let me pull a shot or steam some milk when they aren't busy (think mid-afternoon, after the "post-lunch rush").
Finally, as I often tell my 13-year old, "It's not your job." In her case, I often need to remind her that we are the parents, and it's not her job to be a parent to her 11-year old sister; in your case, it's not your job to "raise the bar" of the B&B's espresso. Not only isn't that your job (your job is to be that of a guest, not a barista), but -- again -- you run up against the ego thing.
Cheers,
Jason
P.S. I don't understand one thing you wrote. "The man said his brother owns a La Pavoni, so I was quite mystified by the experience." While that's fine, why would that make
him (as opposed to his brother) good at pulling shots? Isn't that a bit like saying
My brother is a race car driver; how come I keep getting into traffic accidents? 