When I go on rec dive trips I simply tell my instabuddy that I would be giving the reg from my mouth.
This has been easily understood and not been a problem.
An out of air diver wont be fussing about an offered working regulator, he'll be too happy to take it.
Practice the S-drill by yourself, switching to your second and unraveling your long hose, to build up muscle memory.
I wish you the best on your stay in paradise, I hope to visit this area one day.
Two out of three times the average recreational diver when confronted with a true OOA will take the reg in your mouth anyway regardless of how they were trained. If/When that happens, you are better off with a long hose primary configuration as it 1) gives you a bit more room to move and swim more or less normally, 2) will virtually eliminate the tendency that a short hose has to pull on the reg and increase the panic level of the OOA diver who feels he may lose the reg and 3) finally, the bungeed octo is very easy for you to find when you sudenly lose your primary.
The only real caution would be to go with a folding snorkel in a pocket if you feel you may still want to have a snorkel to eliminate any interference with long hose deployment. Also, hose lenght may depend to some extent on the rest of your configuration. If you have a back plate and wing, just go with a 7' hose and tuck the extra in the waistband. If you have a more recreatioanlly oriented BC with no waistband, go with a 5 or 6 foot hose so that the extra unsecured lenght is not a problem.
Coming from an outsider that is eventually going to convert to the long hose/bungee backup and occasionally lurks here .. I've highlited the areas that I think will answer/help you in your transition.Kathy, I travel with my long-hose setup all the time. Be prepared to deal with some curiosity from people who've never seen one before, and perhaps some gentle ribbing from dive staff. And don't let them set up your gear if you can help it ... (lots of places consider it a "service").
What I will do if I'm hooking up with a buddy I haven't dived with before is show them how it works ... i.e. "you give me an OOA signal" ... and then show them how it's donated. That usually gets a "that makes a lot of sense" response, and there are no language barriers with a demonstration.
As others have said, go with what makes you more comfortable.
... Bob (Grateful Diver)
I think that donating the reg in your mouth makes sense, for many reasons, one being that the reg your handing off will be water free and ready to breathe.
I already have a rec. config. that requires me to donate my primary, and I put it on a longer hose to make that easier