I travel throughout Latin America a lot with my camera equipment. I carry everything in a camera backpack. I always pack my tripod in my checked in suitcase though and any liquids for lens cleaning I put in plastic bags, just in case. Only once have I had a problem with backpack size where they made me check in the back pack at the door, in that case I took the camera out and carried in on my lap. I wouldn't worry too much unless you are taking some small airlines internally within the county.
Keep a hand on your bag at all times, I even put my foot into the loop of my backpack when I am at the checkin counter. I have friends who have lost their briefcases by setting them down at checkin counters.
OK I travel a lot with my camera equipment as well and I have a suggestion. If you are taking a back pack, I do, consider disconnecting the lens from the camera body and protecting them both individually. It makes it easier to place in overhead on smaller planes and lessens the chance of damaging the lens connector points. I agree with all of the other posts about security as well. The X-ray will do no damage to your cards, I'm completely sure of this. Enjoy!