I was in a similar situation as you several months ago because I recently graduated. I debated on studying for the GMAT but ended up not studying because I simply did not have enough time.
I think an important factor to consider is how much time you have outside your school obligations. Are you involved in extracurricular activities? If you are, chances are it might be very difficult for you to do well on the test with everything going on in school. It is possible to do well but you will have to greatly sacrifice your free time and/or social life. You also have to at least maintain your GPA because there is a risk. I mean, your GPA could decrease while studying for the GMAT and you do not know whether the time you invested in studying for the test will be enough to get score that you need. If you are confident that you will get it all done, go for it. If not, think about whether you can take the risk.
It will probably be less stressful to study while in college than to study while working in IB...if that is even possible knowing you will have to work like 100 hours/week if you are in US or UK.
One last alternative is not to travel and use the time to study (I hate how I ruin all the fun). Another thing you need to have in mind is that most people study 3-4 months and take the test. Most people who did well usually study over 20 hours/week. You can check this information in greater details in other thread.
If you choose to study, make sure you get prep books and not just the ones issued by the GMAC.
Good luck man, hope you make best decision for you
Set your aims high, carpe diem