Accepting or Declining an Invitation

Someone invites you to do something and you respond — whether you can make it or not.

Friend
Mañana vamos a la playa. ¿Vienes con nosotros?
mah-NYAH-nah VAH-mohs ah lah PLY-ah. VYEH-nehs kohn noh-SOH-trohs?
Tomorrow we're going to the beach. Are you coming with us?
You
¡Me encantaría! ¿A qué hora salen?
meh ehn-kahn-tah-REE-ah! ah keh OH-rah SAH-lehn?
I'd love to! What time are you leaving?
'Me encantaría' (I would love to) is an enthusiastic, polite way to accept any invitation.
Friend
Temprano, como a las nueve. ¿No tienes otros planes?
tehm-PRAH-noh, KOH-moh ah lahs NWEH-veh. noh tee-EH-nehs OH-trohs PLAH-nehs?
Early, around nine. You don't have other plans?
You
En la mañana estoy libre. Pero en la tarde no puedo, tengo un tour.
ehn lah mah-NYAH-nah ehs-TOY LEE-breh. PEH-roh ehn lah TAR-deh noh PWEH-doh, TEHN-goh oon toor.
In the morning I'm free. But in the afternoon I can't, I have a tour.
'No puedo' (I can't) is the simplest polite way to decline. Adding a reason like 'tengo un tour' softens it.
Friend
No te preocupes, regresamos temprano. ¡Va a estar divertido!
noh teh preh-oh-KOO-pehs, reh-greh-SAH-mohs tehm-PRAH-noh. vah ah ehs-TAHR dee-vehr-TEE-doh!
Don't worry, we'll be back early. It's going to be fun!
'No te preocupes' (don't worry) is one of the most useful reassuring phrases in everyday Spanish.