TWENTY APLENTY: About one-fifth of the county’s...

TWENTY APLENTY: About one-fifth of the county’s population is made up of people in their 20s--nearly half a million in all--and their greatest concentration is in Aliso Viejo. . . . About one in four residents there is in the 20 to 29 age range, and that’s no surprise, says the developer’s spokeswoman: “Entry-level buyers are our target market.� . . . Most buy condos or townhomes for a median price of $160,000, nearly $8,000 less than the countywide figure. . . . No shock then that pricey Coto de Caza has the lowest proportion of the 20s--about 8% of residents.