What is the difference between these two words, or are they the same?
人缘儿 and 谈得来 Am I supposed to use them at different times?
人缘儿 means "popularity" (in a casual situation).
他很有人缘/他的人缘很好 means "He is very popular" or even simpler "He has many friends"
Especial, 他很有女人缘 means "He is very popular among the girls" or simpler "He attracts girls"
谈得来 basically means "easy to build a conversation with". So it is about two or a very small group of people. Basically means the mentioned people are close friends and often spend time together.
我跟他谈得来 means "He is the one I'd like to talk to a lot." or simply "he is my close friend."
几个互相谈得来的朋友 means "some close friends"
There is a quotation in Chinese saying "酒逢知己千杯少，话不投机半句多" means, "If I meet a close friend, I can drink thousands of cups of wine while talking to him, but still not satisfied. If I meet a person that I don't like, I feel like speak half a sentence to him is a waste of time." So "talk to a lot" = "close".