General Brazilian
multidão, turma, galera
galera is commonly used for 'group of people' in casual speech
Rio de Janeiro
galera, povo
colloquial usage; 'povo' can mean crowd informally
São Paulo
multidão, galera, pessoal
pessoal is used for informal groups of people
Portugal
multidão, ajuntamento, pessoal
ajuntamento is more formal; pessoal for informal groups