Yes, the Home Clans ward away all but the most desperate of anyone; pirate, trader or mercenary.
The upper crust and those who work to preserve knowledge would probably learn Star League English, as it would make sense to want to be the one who does control outside contacts at the expense of those who cannot. Always a good position from which to bargain. But that would probably just be a small relative handful of the population.
That was my take. Love seeing the map, as always.