In won't take you a longtime into your visit to Mexico to discover to what extent the Mexicans are friendly and welcoming. The country is so big and the population is so different that everyone doesn't follow the same rules of politeness and the same daily lifestyle uses.
Whatever the region in this immense country you will discover during your trip to Mexico that the inhabitants place a large importance on family. A true cult is vowed to it. It's the same thing with regard to religion. The Mexicans are very pious and their religious fervor is very important. Mexico is also the country of parties. In all the towns, for each daily life occasion, the Mexicans don't hesitate to get out musical instruments, the flags and the garland and they organise large parties in the streets. It's impossible to go across the country without attending one of these. It is also the best way to discern just how welcoming and friendly the Mexicans are. They love talking, arguing and chatting. They excel in this art of the gift of the gab, and they don't hesitate to throw in jokes and a number of compliments. When they address you saying "Es tu casa!", that is to say "It's your house", you can consider yourselves definitively adopted. Don't forget that it is always bad to get angry or to make a scandal, whatever the reason. That isn't the done thing and you will always be better received when you show yourself as friendly and smiling.
In the very touristic places, in certain very poor quarters of large cities or in the more secluded villages, you will be (due to your status as a tourist) very often asked by children or beggars for money. It is difficult at times to know which attitude to adopt in this type of situation. The ideal would be to refuse so as to not encourage begging, overall when dealing with children. Their place is more in a school than in a road or certain parents prefer to send them to collect some money. It remains without doubt better to make your donations to an ONG or organisation who will already be working in the country. Your money will thus be used in a much better way and knowledge.