There are a LOT of areas in SD County with SFR’s <$250k. But they are not in the most desirable areas. They are not in areas that most people that live by the beach have probably ever been.
You can get a totally rehabbed 3/2 1,200-1,500sf house built between the 1940's to 1970's for about $250k, and a 3/2 fixer for say $210k in these areas.
-El Cajon
-Santee
-Lakeside
-Old Chula Vista
-Paradise Hills
-Lemon Grove
-Spring Valley
-National City
-Encanto
-City Heights
-SE San Diego
-Oceanside
-Vista
-Escondido
-San Ysidro
-Many parts of the College area
There are all more working class, blue collar areas. If you want to get into a white collar area with the very top schools, yes it is going to be $350,000 on the very, very low end for a fixer and more like $500,000 for a fixed up house.
You can get condo's pretty much ANYWHERE for $250k or less. Even in places like Carlsbad, Scripps Ranch, Rancho Bernardo, Point Loma, PB, etc... And that is even 3/2 condos!