Complex sentence: Although these kinds of organizations of have existed in Mexican communities since the 1950s, the numbers have expanded dramatically over the past two decades; there are now well over 600 Mexican hometown clubs and associations registered in 30 different cities throughout the United States.
Split into simpler sentences: Although these kinds of organizations of have existed in Mexican communities since the 1950s, the numbers have expanded dramatically over the past two decades. There are now well over 600 Mexican hometown clubs and associations registered in 30 different cities throughout the United States.