I have travelled lots around the world, and taken thousands upon thousands of photos with my DSLRs in various situations. From several countries within Europe to SE Asia to many parts of Australia (where I grew up, now live and have returned after sevearl years abroad).
Convenience is important while on the go - I want to enjoy my time of walking, travelling, seeing sites, talking with people and yes, also photographing lots. But I would opt for a light & available body with a zoom in most cases than travel rather than feel like a 'fully laden pack horse' with a host of lenses, including too many primes!
In your case, I'd probably opt to buy a 24-105mm L, and use the 16-35mm time to time too. The 70-200mm f/2.8 II is a great lens, but very heavy to take along. I can see the new 35mm f/2 IS being a great option as a 'street photography' / low light option too.
I use a 7D as my travel camera, and the Canon 15-85mm is my main camera. So yes, it does depend on each individual's photography style, but I would expect that many photographers would find the 24-105mm on a 5DmkIII the most handy combination (or the newer Canon 24-70mm f/4 IS as another travel option).
When I go for 2 lenses, it's often the Canon 15-85mm and Canon 70-300mm L. A great, and very portable 2 lens travel solution - providing very high quality images. Though in some situations I'll (also) take and use my Sigma 8-16mm (love that ultrawide!) Of course one can use all 3 lenses as such if that is preferred.
When I was on holiday in Thailand some time ago, I used the 15-85mm about 80% of the time on my 7D.
Thanks for the input
The thing is that I'm aiming mostly to shoot for new clients and for my portfolio and less vacation-shooting so I'm willing to bring some extra lenses if it makes my eventual clients more happy.
Yes, the 70-200 is quite heavy, but maybe 200mm will come in handy sometime? Its so sharp and have such nice reach
the 135 is also very nice and a lot lighter. Equipped with 1.4" its quite long aswell. I'm shooting on FF so it's not as long as with the 7D though.
The 70-300 seems to have a nice range, but it's quite expensive aswell
I've looked at this before.. just trying to justify the cost.. hehe