Cheap Apartments For Rent In Downtown San Diego . Cheap apartments in san diego; 2,358 affordable apartments for rent. The Leo Apartments For Rent in San Diego, CA from www.forrent.com We found 48, studio bed apartments for rent in the downtown san diego neighborhood of san diego, california. The average apartment rent in san diego county is $2,467 per month so any rental south of $1,973 would be considered cheap here. Downtown san diego cheap apartments.