Must try harder
"you need to hack the coffee shop's router" - no you don't. You even explained why this not necessary in the preceding paragraph.
"Certificate pinning, though, is limited to Google sites at present" - no it's not
"Some browsers such as Chrome use a new technique called certificate pinning" - That would be Chrome, Midori, Firefox, Opera, but not MSIE/Edge currently (not aware of status of Safari).