I recently went Korea for a holiday and brought my PnS, DSLR and 2 lenses. If your trip is around a week with cool weather, it's safe to just keep it in the camera bag. If you're staying for longer durations and in humid weather, u may want to put silica gel inside.
What country? If the climate there is dry, then you won't have a problem. Fungus growth happens over years anyway, so vacations to most countries for a month or so shouldn't be a problem. Go to a really wet place like the Amazon and you'll have to worry about some serious condensation when you take out your camera, though.
But anyway, portable dry boxes exist, for you to store your camera and carry it around.
brought my dslr to ho chi minh recently. I just keep in my camera bag, shouldn't be a problem. Like someone mentioned, thievery is more of a concern. When i was shooting, the locals were like staring at me.... some with intrigue, while others i am not very sure..
even in singapore, its ok to leave camera outside dry box if you are using e lens/camera. if i know i am gonna shoot quite alot, i don bother to keep the lens in the dryboz and taking it them out again...troublesome. just leave them in the bag.
just think of leather goods like wallet, if you keep using it there will be no fungus. but keep in a humid plac for a month and fungus will appear. fungus needs time and bacteria also need a stable home! keep moving and shaking the lens the fungus wont have a chance
In temperate countries, dry box not very necessary. That's why they don't even need to put their opened boxes of cornflakes in Tupperware - won't "lao hong" one! I was in Brisbane Australia for 4+ years and I never used any dry box, no problems. However, do note that dry climates give another problem: Static charge tends to build up rather easily, making things become dust-magnets, so take extra care when changing lenses on your DSLR.
Would like to know what is the reason? the bag is made of fabric not plastic? I put the lense bag is to prevent the lense body from rubbing aginst the camera body, alternatively, one can use a piece of form in between as protection, but I though the bag will be neater.