Translation:To the north, to the south, to the east, to the west
I think "northward" etc are adverbs (they describe verbs), whereas "northerly" etc are adjectives (they describe nouns: "We continued northward, with a northerly wind blowing in our faces." So in this question you could say northward etc, but not northerly etc, because the Esperanto words to be translated are themselves adverbs.
Northerly, southerly, etc. can both be adjectives and adverbs.
New Oxford American Dictionary says, in particular, the following:
adjective & adverb
in a southward position or direction: [ as adj. ] : the most southerly of the Greek islands | [ as adv. ] : they made off southerly.
• (of a wind) blowing from the south: [ as adj. ] : a southerly gale | [ as adv. ] : the wind had backed southerly.
Because of the tone of his voice I wrote "Norden? Suden? Orienten? Okcidenten?" :)
I don't think informally means incorrectly, so I don't reckon you can just leave it out. People probably will informally, but that doesn't mean they should.
I went to an Esperanto study weekend and one of the older fluent speakers always said things like “ĉu teon?” when people were getting something to drink and he asked “tea?”. (I reckon it's short for “Ĉu vi volas teon?”; not entirely sure whether he used the accusative case; it was a while ago.)