What language to learn...it really varies by company and where you want to go during your career. Portuguese is pretty good these days with lots of stuff happening in Angola and Brazil, both of which are Portuguese speaking. Spanish, Dutch, German, Czech, Russian, French Japanese, etc. Oil is completely global and if you know a language you certainly could work that to go to a location. My advice, pick a language for a place you want to go. If you really want to work in Rotterdam then learn Dutch, etc.
I dont think many people who end up in oil have had long standing dreams about going into it. There are lots of things to get you excited about it. The career path is interesting, you will see a lot of cool things during your career and the scale of things is amazing. You could be dealing responsible for billions of dollar several years out of school. It is probably the most global industry in the world, the major oil companies operate in almost every single country on earth...the only ones they don't are usually because of political reasons or they are so unstable its not worth the risk.
Career progression can be very impressive, the pay and benefits are top notch...how many places still have pension plans and match 7% on your 401K. They tend to be towards the high end of the pay scale when you graduate and as you advance the pay increases are substantial. You will be treated as a high potential person who is expected to reach the executive ranks, and thus you get a lot of attention and responsibility.
The GM path at some companies is also one of the most broadbased things you will ever do. Not many places will put you incharge of marketing, then move you into a supervisor role at an industrial plant, then make you a trader, then put you in an operations role, and if strategy interests you then they may just stick you in that too. I have seen people who have just such interesting career paths and all within 10-15 years.