Downtown San Diego Towers owned by Irvine Company go for 50% of purchase price when office vacancy is at 35%. After buying 93000 acres of coastal Orange County in 1977 and building office towers in San Diego, David Bren now 93 years, is offloading most of his investments in San Diego at half the price paid for it. This and the quality of life and homelessness in the downtown area of San Diego is depressing prospects for the city which is now dependent on the biotech sector.