If I owned only a 50, I would travel with it. One size fits all, problem solved. As it is I have 16 Nikon lenses, so it's a no-deal. I've always found the 35 to be not quite wide enough for my eye and the 50 too limiting for my view of things, so I'd pack a 28.
These days I get about in Asia with a D700, a 28 and 85, hoods, UVs and a (rarely used) polariser. That's it. For many years I shot with a 28-85, but last month it finally rendered up the spirit, and given its advanced age I won't have it repaired or replace it. I'll make do with my two primes.
If I had to take a third lens, it would be a Micro Nikkor 60. A fourth, a 180.
The problem for me with threads such as these, is that most posts raise points/make arguments that make good sense. In the end, it all boils down to what suits the traveler best. Me, it's 28 and 85.
I traveled throughout Southeast Asia with a Nikkormat FT2 and a 50/2 Nikkormat in 1993 and did a repeat journey with this kit in 2006 (the latter was my last entirely film project). During both journeys I shot thousands of color slides - the film I carried with me weighed much more than the camera kit. In the '90s, one could still make good money from stock, and my 'standard lens shots' (largely portraits of Asian women working at traditional occupations) sold enough to pay my airfares. The (very few) landscapes/town scenes I shot have been long forgotten. So if your shooting tend to these, the 50 may not be your best choice. Nowadays, stock has hit rock bottom anyway, so all this is really nostalgia, for what it's worth.
Yes, let's travel with our camera(s), and one (or more) lenses. But enjoy the journey, the new cultures, the experiences. Look, see, learn - and make images along the way, as you go.
An excellent (if somewhat dated) thread, seemingly revived by some divine act, like the return of Lazarus. I somehow missed it in 2010, this time I'll follow with interest.