YMMV, but here are some more specific places I would not want to live:
PART ONE: Avoid the whole county:
ORANGE COUNTY
Avoid the whole county, in particular:
Westminster
LOS ANGELES COUNTY
Avoid the whole county, in particular:
Bell
Bell Gardens
Bellflower
Carson
Commerce
Compton
Cudahy
Hawaiian Gardens
Huntington Park
Industry
Inglewood
Irwindale
Lakewood (west side)
Long Beach (west side)
Maywood
Montebello
Monterey Park
Paramount
Pomona
Santa Fe Springs
Signal Hill
South Gate
Vernon
RIVERSIDE COUNTY
Avoid the whole county, in particular:
Banning
Blythe
Corona
Hemet
Indio
Lake Elsinore
Moreno Valley
Norco
Perris
Riverside
SAN BERNARDINO COUNTY
Avoid the whole county, in particular:
Adelanto
Apple Valley
Barstow
Colton
Hesperia
Needles
Ontario
San Bernardino
Victorville
KERN COUNTY
All
SAN BENITO COUNTY
All
PART 2: Nice counties with some pockets to avoid:
SAN DIEGO COUNTY
Chula Vista
El Cajon
Imperial Beach
National City
San Diego (San Ysidro area)
VENTURA COUNTY
Simi Valley
Oxnard (El Rio area)
Saticoy
ALAMEDA COUNTY
Oakland
SAN FRANCISCO CITY & COUNTY
Tenderloin
Upper Haight
PART 3: These places seem nice all around, but I haven’t lived there:
SANTA BARBARA COUNTY
Santa Barabara can be a bit snooty though.
SAN LUIS OBISPO COUNTY
MONTEREY COUNTY
SANTA CRUZ COUNTY
PART 4: I’m not very familiar with:
SAN MATEO COUNTY
SANTA CLARA COUNTY
CONTRA COSTA COUNTY
From what I have seen, they look boring.
SACRAMENTO is beyond the scope of the OP. I would agree that it’s hot, but I don’t think it’s “dirty” or “gross”. If you don’t mind a bit of heat, it’s a nice place.