It seems like Duolingo is using Northern pronounciation
I live in San Jose, CA and would prefer to learn with the Southern accent that is used in the Vietnamese community here. Is there a way to switch?
There's no way to switch. Someone's regional dialect needs to be the standard, and in Vietnamese it's the north's.
It's really not that big of a deal though. The only big difference is between the northern z sound and the southern y sound. With words like dễ, rẻ and giỏi, just keep a mental note to pronounce them with a y if you want the Saigon accent.