Welcome to Bay Area! Yes, you just need to go the banks and you can get changes. However, if you expect to get quite a bit, says a few hundreds/thousands worth, some banks may need to order that for you. Better to go to the bank way ahead, don't wait until the last week. Some banks need to order from regional office and it may take 3-5 business days. Otherwise, you may need to go to several banks to get all you need. I know people working in branches and they usually suggest to prepare earlier.