I can't speak Japanese [well].
Nihongo [yoku] hanasemasen. (nee-hohn-goh [yo-koo] hah-nah-seh-mah-sen)

Do you speak English?
Eigo o hanasemasuka? (AY-goh oh hah-nah-seh-moss-KAH?)

Is there someone here who speaks English?
Dareka eigo o hanasemasuka? (dah-reh-kah AY-goh oh hah-nah-seh-moss-KAH?)

I don't understand.
Wakarimasen. (wah-kah-ree-mah-sen)