Can you choose to be gay or bisexual?

No, homosexuality is something you are born with, much like heterosexuality or feet.

(edited to show the information below is not associated with that above)

I am not sure you are grown with it some people are but you can just get that way.. you don't choose it you just start getting attracted to the same sex most people turn bisexual then gay.

-Note, bisexuality is not always a stop on the road to homosexuality.