Asking If Someone Speaks English

You need to switch languages and ask if the other person speaks English.

You
Disculpe, ¿habla inglés?
dees-KOOL-peh, AH-blah een-GLEHS?
Excuse me, do you speak English?
Always start with 'Disculpe' (excuse me) — it's polite and gets the person's attention.
Local
Un poquito, no mucho. ¿En qué le puedo ayudar?
oon poh-KEE-toh, noh MOO-choh. en keh leh PWEH-doh ah-yoo-DAR?
A tiny bit, not much. How can I help you?
'Un poquito' is the diminutive of 'un poco' — it means 'a tiny bit' and is very common in everyday speech.
You
Necesito ayuda. Mi español no es muy bueno.
neh-seh-SEE-toh ah-YOO-dah. mee ehs-pah-NYOHL noh ehs mooy BWEH-noh.
I need help. My Spanish isn't very good.
Local
No se preocupe, le ayudo. Hable despacio.
noh seh preh-oh-KOO-peh, leh ah-YOO-doh. AH-bleh dehs-PAH-syoh.
Don't worry, I'll help you. Speak slowly.
You
Gracias, es usted muy amable.
GRAH-syahs, ehs oos-TEHD mooy ah-MAH-bleh.
Thank you, you are very kind.
'Es usted muy amable' is a warm, respectful way to thank someone who's gone out of their way to help.