回复：急问：父母绿卡入境后手续问题

No, they can choose whereever in the 50 states or DC they want to become residents of. They should get SSN, Cal state ID (or DL),... soon after landing.
MediCal, they won't be able to get this in five years, and also, Medicare (part A) is not free for them. After 1996 new law, the I864 sponsor will be responsible for repaying the welfare back to government if your parents use it in the five years.