Move to the US, come to Arizona, and become a drummer...My band could use one!
Nah, but seriously...Singers, Drummers, and Keyboardists are very hard to come by, especially where I live. We have a surplus of guitarists, and most of them suck more than I do (And I suck pretty bad).
Here's a few things to think about:
Do you have power in your voice?
Could you pick up on ear training quickly? if yes to both, then singing might be for you
Do you have strong legs and arms?
Do you have good hand-eye coordination? If yes to both, drums would be a good choice
Do your fingers move fairly well independently?
Could you pick up on sight reading easily? If yes, keyboard might be a good choice
Note: Those are just a few of the deciding factors you should take into consideration, anything like that which I listed could help you learn your instrument of choice much quicker. It's up to you, I personally play guitar, drums, and sing, but if you want to just stick with one, I'd say try and figure out which would best suit you. Personally, I think singing is the hardest one to decide on, in that it's tough to determine whether someone has a good singing voice based on lack of knowlege of them. If you choose singing, try either joining a choir (school, church, or otherwise), or take private lessons.
Good luck