Humans are sometimes a little dense. They may not understand that you're just as interested in seeing the world as they are. Because of this unfortunate fact, you may need to resort to subterfuge if you're ever to get out of the house.
It's true that there's a greater chance your humans will notice before the trip commences if you stow away in the carry-on luggage. However, this risk is worth taking, since otherwise you will be stuck in the cargo hold during the flight. Minimize your chances of detection by sneaking into the carry-on luggage just before they leave the house to begin the trip.
If your humans use Eagle Creek Pack-it cubes to organize their clothes, these are an especially good place to stow away if you don't want to be discovered until after they arrive at their destination. Because they're full of clothes, they make a very warm and snuggly den. Ziploc bags aren't as good because you can't breathe inside of them.
Why did you bother to come all this way, if you then spend every day hanging out in the lodgings? Assert yourself -- if your humans don't take you sightseeing on their own, hide out in their day packs. Be sure to choose a position where they'll notice you when they go for a new film cartridge; this will probably be at someplace interesting. Then, put on an especially cute expression so they'll take you out and show you the sights.