Perfectly safe. You do need to be a bit careful going into the sea (like anywhere around here), as Marty says Stonefish are a bit nasty, jellyfish, that kind of thing. I've worked at universities abroad for the last few years (Middle East, Germany) so it's an extension of that.
The British/French shared the administration of the islands until around 1980, so in Vila people generally speak English or French, usually both. The Ni-Vanuatu people collectively speak a language called Bislama, an English Creole, which is really interesting - like a pirate mix of English (and some French) with a strong local accent. For example if something is broken its 'buggerup'. New objects are given literal translations - a 'bra' in Bislama is 'basket blong titties'. My favourite is the word for helicopter - 'mixmaster blong Jesus Christ', which you can sort of work out how they got there.
