You will be fine with a Defy, they are more of an endurance bike, so it will be a lot more comfortable that a race bike. Don't worry about people that stay STIs are hard to fix, although this is true, I have been riding STIs for 10 years now and have never had one fail on me, on top of that you're touring state side not in the third world so bike shop will be able to help you out. I have tourer on both steel touring bikes with trekking groupsets, and carbon bikes with Ultegra road groupsets, and I much prefer touring on my carbon bike.