First of all, a Muslim should be good with all people. A Muslim may have non-Muslim friends and professional acquaintances. However, he has to keep his Islamic identity and set a good example for them in morality, goodness and gentleness. He has to observe the Islamic ethics in all aspects of life. Prohibited foods and drinks should be avoided as well as all other aspects of un-Islamic items and values. By doing so, he will translate the Islamic teachings into practice and at the same time call them to Islam, the religion of morals and goodness. Based on this, a Muslim can go with his non-Muslim friends to a restaurant but he has to observe the rules of the Shari`ah in foods, drinks, etc.
Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states the following: So long as the meats are coming from the People of the Book and so long as they do not contain pork or its by-products then it is not at all forbidden or haram, and so long as they are not cooked in wine or other ingredients that are considered purely haram.
Most scholars of the past, belonging to the four schools, have ruled that meat of the People of the Book are lawful for us to consume based on the Qur’anic verse, (This day are (all) good things made lawful for you. The food of those who have received the Book is lawful for you, and your food is lawful for them.) (Al-Ma’idah 5: 5)
this verse, according to Ibn `Abbas, refers to the meat slaughtered by the People of the Book (i.e., Christians or Jews). We find in the sources that the Prophet’s Companions used to eat the food of the Christians and the Jews whenever entered their territories.
having said this, however, I must add: If you have a choice of going for meats provided by Muslims and those that are served by non-Muslims, you should definitely go for that which is provided by Muslims.