For whatever its worth, IRUSH, I took Spanish in public high school, and lived in a town half Mexican in population, and then went to Guadalajara and studied during my summers of college, and studied more Spanish during my college academic years. I lived in Costa Rica for two and a half years also.
I speak Spanish as well as I do English. I am grateful for having learned the language. I studied Latin for two years in college as well, and lost most of that, and I'm trying to get that back now.
My knowledge of Hebrew is poor, just enough to get me through the Prayer Book without looking like a total schmuck in services. I can't read the alphabet, though.
I think you are right that Spanish or Mandarin Chinese are your best bets. Certainly Spanish is going to be hella easier. Latin is a good choice if you wish to have an appreciation for our cultural patrimony, and if you wish to understand the grammatical base of European languages generally. And of course, if you get Latin, learning Spanish (at the same time or later in life) will be simple.
So, that is where I would rate things. Overall, if I were you, and I had to make a choice based on a purely utilitarian grounds, and had a gun pointed at my head, I would pick Spanish. I think that would be the best option if the above situation obtained.