Complex sentence: In its earlier days the Excelsior was largely Italian, Irish, and Swiss, and today it is one of the most ethnically diverse neighborhoods in San Francisco, with many Asians, Latinos, and other groups settling there in recent decades.
Split into simpler sentences: In its earlier days the Excelsior was predominantly Italian, Irish, and Swiss. Today it is one of the most ethnically diverse neighborhoods in San Francisco, with many Asians, Latinos, and other groups having also settled there in recent decades.