You really shouldn't have any problems. I always disclose that I'm wearing a pump beforehand, as the pump cannot go thru x-rays or body scans. So far I've just been waved through the metal detector, sometimes encounted mild curiosity. I have a letter from my endo and one from animas, gathering dust in my passport wallet.
Always carry your insulin with you - it can freeze in checked baggage. Some airlines allow you to take an extra bag for med supplies. I always carry at least 2 days' supplies with me just in case, and overall double what I think I'll need for the trip.