Wa `alaykum As-Salamu waRahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
Answering your question, Sheikh `Abdullah ibn Jibreen, the late prominent Saudi Muslim scholar, stated:
It is allowed to mix with the non-Muslims, sit with them and be polite with them as means of calling them to Allah, explaining to them the teachings of Islam, encouraging them to enter this religion and to make it clear to them the good result of accepting the religion and the evil result of punishment for those who turn away.
Almighty Allah knows best.
Source: Islamic Fatawa Regarding Women, Compiled by Muhammad Ibn Abdul-Aziz Al-Musnad and translated by Jamal Al-Din Zarabozo, Darussalam, 1996.