Default currency / pricing group based on user country or audience

It seems that, in Oracle Commerce, logged-out users always see prices in the default currency.

I'd like to have our store show prices to logged-out users based on what audience they're part of; for example, USD for people in America, GBP for people in Britain, etc.

What's the best way to go about this?

I could do it in a widget; just have a widget on every page that makes a REST call to find what audience the user is in, and sets the site().selectedPriceListGroup observable based on that.

However, I would expect this to be a bad user experience, because the site would load in the default currency first, before changing to the new currency when the REST call returned.