The expat network Internations does a survey each year amongst its members, ranking countries on a number of criteria, one of which is “Finding Friends and Friendliness.” Coming in first place in this year, up one position from last year, is Mexico.
They report, "almost all expats in Mexico (94%) rate the general friendliness of the local population positively, and more than half (56%) believe that attitudes towards foreign residents are very friendly. A large majority feel at home in the Mexican culture (85%), find it is easy to settle down there (85%), and have few problems getting used to local customs (83%). More than half (55%) do not struggle to live in Mexico without speaking Spanish, and just under two-thirds (66%) consider learning the language simple.”
Other countries found to be friendly were Bahrain, Serbia, Costa Rica, Ecuador, Uganda, Colombia, Taiwan, Israel, and Portugal. Countries found to be the least friendly, or hardest to make friends, at the bottom of the list were Sweden, Denmark, Switzerland, Saudi Arabia, Germany, Norway, Finland, Austria, and Estonia.
You can see the full results here. Internations was founded in 2007 and currently has 3.5 million members in 420 cities worldwide.