Use the minimal UI config file hack and disconnect from the internets after entering your chosen world (reconnect again before saving), mission accomplished.
Disconnect from the internet after starting your ride and everyone else will disappear. Reconnect just before finishing your ride so that it will be uploaded at the end.
Alternatively you can also just create a meetup (need a second user for that, create a dummy account if you can’t think of anyone who will ignore your invites…) and select the only meetup riders visible option. Or even using the world hack and picking one of the worlds outside of the three in the daily rotation usually means you won’t have too much company.