my doctor prescribed me adderall xr but it's really expensive since there are no generics. do you think the pharmacy will let me buy the "reg" adderall generics or do I need to get another prescription from the doc?

You will probably have to get another prescription from your doc.
You could try and have the pharmacy call your doc and approve the generics maybe.

my doctor prescribed me adderall xr but it's really expensive since there are no generics. do you think the pharmacy will let me buy the "reg" adderall generics or do I need to get another prescription from the doc?

You will need a new prescription, they have to give you exactly what is on the prescription. I would be sure to bring your old script into the doc to be safe just in case he wants it back as I'm not sure if he is liable for it if he writes you one for the immediate release. I would also tell him you want generic, I think they have to indicate on the script if generics are allowed.