Learn Russian: Мы едем на юг.

In Russian, verbs of motion change depending on how you travel. Идём means going on foot, while едем means going by a vehicle (like a car, train, or plane). Since people usually travel long distances to the south using transport, едем is the correct choice.

Why is the preposition на used here instead of в?

While в often means "to" or "into" a specific place (like a city or a building), Russian specifically uses на with compass directions. So, you always say на юг (to the south), на север (to the north), and so on.

Since "south" is our destination, shouldn't юг change its ending?

It actually is in the accusative case, which is the grammatical case you use for destinations! However, for masculine nouns that are non-living things (inanimate) like юг, the accusative form looks exactly the same as the regular dictionary form.

Does едем mean we are going south right now, or that we travel there often?

It means you are on your way there right now (or are taking a specific, one-time trip). Russian uses a different verb (ездим) to talk about going somewhere regularly, like going south every summer.