I'm always glad to hear from another female interested in civil engineering.
I'll do the best I can to give you my opinion relative to your question.
I am sure there are structural engineers who do get to travel to potential project sites, and projects under construction. However, in all honesty, the typical structural engineer does not do a lot of international travel, at least in my experience. If that is what you desire, it will be important for you to do research on the companies that offer structural engineering on projects throughout the world. This could a an engineering company, or it could be a construction company that does design/build projects.
I would basically have the same answer for architecture -- the amount of travel would depend totally on the company you go to work for. The average architectural firm will do more local projects, but there are firms out there who are sought after for projects throughout the world.
One plus of structural engineering over architecture is your starting salary -- architects typically start at a lower salary until they are licensed, whereas engineers can make a pretty good starting salary before getting their professional engineer's license.
I urge you to take some time to look again at your interests, personality and strengths as you choose between these two professions, as they are very different. If you are looking for more of a creative outlet, and greater overall project management opportunities, then architecture would be a better fit. You find more introverted, scientific personalities in structural engineering (although I am a structural engineer and an extrovert).
Another option is a major that some schools like Penn State offer -- architectural engineering. That gives you the best of both worlds.
I truly believe that a degree in structural engineering is a great basis for a variety of careers, and if travel is what you want, you should be able to find that opportunity with some searching.
Hope this helps,