For what its worth, I live in Florida where humidity is really bad. I can walk out onto my backyard and get condensation immediately. Same thing happens at the zoo or any outdoor location when I take my camera out of the bag. I don't have the patience for the plastic bag trick 
I just keep a microfiber cloth to immediately wipe the lens/filter when this occurs, and then shoot as normal.
I've had no issues with the camera (Rebel XTi) and i have had it since 2006 or 2007, can't remember but it was pretty new back then.
Also had my film Rebel (Rebel 2000) in Hawaii with mist, rain, the works. I even fell in mud, camera in hand, while hiking down a steep path towards a black sand beach on the big island. Wiped off lens and was good to go, got some great shots. Funny enough I still have my old film Rebel, although it's no longer in use, and to this day it has mud that I couldn't get out of some of the really small areas - call it battle scars! 
The best suggestion I agree with in this thread is not to change lenses in such conditions. If the mirror condenses, you might clean it but you also risk getting dirt and debris on it which will end up in your photos.
I suppose if you want to go all out, you can get an underwater case for the camera (if available), although unless you are planning to SCUBA dive with it, this would most certainly be overkill.