Speaking at an overseas wedding
Utilise the wedding location for humour.
Whilst speaking at an overseas wedding may bring its own challenges in terms of getting over jet lag and remembering to take all the right clothes (and a copy of your speech!), it also supplies you with a wealth of different elements that you can use.
Whilst it's normally not advisable to include in-jokes in your speech - a knowing anecdote about your University days won't be funny to anyone who wasn't actually there, and may in fact upset or annoy others - when the audience clearly has an experience in common it can serve to unite them and instantly make them warm to you.
If, for example, your destination is known for having a chaotic airport, extreme heat, or a particular cuisine, making jokes around these topics will strike a chord with all your audience. Be careful not to be insulting to your location though as it's possible that some of your audience actually live there, so you don't want to start ranting about local mannerisms or customs and risk upsetting anyone. Think about the shared experiences your audience is likely to have had in getting there, or during the few days before the wedding. Make sure that jokes are against yourself rather than the audience, for example:
"Ladies and gentlemen, I'm very pleased to be here to talk to you today, although I may be a little overdressed for the heat; when the Groom told me the wedding was to be held in one of his favourite places in the world, I obviously assumed he meant the bar of the Dog and Duck, not this amazing beach".
"Ladies and gentlemen, to put the nerves and anxiety I have experienced today into perspective, I am delighted to announce that I no longer suffer from squat toilet syndrome."
It helps to know why the Bride and Groom chose the location, and don't insult their choice. Light-hearted jokes about the weather are fine, insulting comments about the difficulty or expense of getting there are not!