I was scanning the answers to see if this would come up, I'm glad Lamont mentioned it. Kathy, I find that a lot of seasoned practitioners forget (or were diligent enough when learning never to run into the problem) that DIR hose routing takes a little extra effort when gearing up than a traditional recreational reg setup. With a "regular" setup, you pretty much just pop the primary in your mouth and make sure you know where your octo is.
With a long hose, you do need to make sure you put the regs on right, and you REALLY should test via an s-drill before getting into the water or descending. In case you haven't used a long-hose setup before, you should first take the backup and bungee it around your neck. THEN, set up the long hose (behind right of wing/shoulder, around your lower right torso up and across your chest up to the left of your neck, around the back of your head to the right, and into your mouth).
You want your backup on first so that its hose remains under your long hose, so you don't accidentally trap the long hose as you try to donate. You want to make sure you didn't forget to put your bungee necklace on. You also want to make sure that the loop of long hose that goes behind your neck is not too big, and doesn't accidentally catch the valve or first stage regulator of your tank.
All of these issues can be caught by performing a mod-S drill after gearing up and before getting in the water; a mod-S is a one-person mock air-share: you essentially deploy the long hose with your right hand (remember to duck your head slightly to let the loop free itself over your neck as you deploy) as you would do towards an OOA diver, and insert your backup reg with your left hand. This will catch any trapping problems that may have come up during gear-up (and if you breathe from your primary and secondary during the drill, you confirm your tank valve is open, too). After fully deploying, you then re-stow, and go diving.
It's probably a good idea to go through this a couple of times with someone who is familiar with the system, it only takes a few minutes. I muddled through a lot of it by myself at first, and everytime I failed to do a mod-S, I'd find out during the dive that I had forgotten one of the things above.
Once you get used to the procedure, it really becomes second nature. But IMO, switching to a long hose without getting a basic run-through of how to set up and use it is more dangerous than just completing your vacation with the setup you're used to, and working out the long hose with a mentor when you get back (but again, if you can get just 30 minutes with a DIR mentor first, this should be a complete non-issue).
