Undocumented people have been able to get the vaccine in California without paying so you can get it and don't need to pay.
According to what I've heard, you can just walk into any Walgreens/pharmacy to get it, without paying or getting an ID check.
Not sure how legal that is though. I understand that those should be for tax-paying citizens.
I wouldn't want to spend so much money flying there without a guarantee. Anyways, I will probably be able to get something (looking for a 3rd Pfizer shot), I just don't like to depend on getting lucky.