Because one goal of 20,000 Dialogues is to encourage interaction between Muslims and non-Muslims, it's a good idea to include a Muslim in your dialogue group. If you don't personally know a Muslim you can invite to join the dialogue, here are several strategies for reaching out:
Do an internet search for "interfaith" and "name of your city" or "mosque," "Masjid," or "Islamic Center" and "name of your city" to find Muslim contacts in your community. Make sure you ask to speak to someone involved in interfaith efforts.
Use Evite, a free service for sending online invitation.