They MUST be protected from 32f. I know there were some Mango hobby growers pre 2007 who had a few types thriving and fruiting in the central valley. 2007 was so cold that the usual frost cloth protection wasn't enough and the tree's were killed outright.
Still, even The Rare Fruit Growers association says Mangos are viable in the central valley...the fast growth from that heat does wonders.
I would advise protecting from all frosts..They can be set back years in growth from one 32f or less night.
Now,in pots its much easier to move them under shelter into the garage..here in the bay area one person I see has a 12' Manila mango in a oak barrel sized pot that he rolls into his garage on frosty nights...and in summer,he places where it gets all day sun.
Mango's are worth a try. I just wish I could convince all who try that...you MUST protect from a hard frost.