Delray Beach zoning question

[Lori Hunter]

My husband and I own a duplex near downtown Delray Beach.  We are surrounded by other multi family properties on our street.  My husband and I were discussing building another unit on our property (yes, there is room), but I just got off the phone with a lady in the city zoning department that explained all these multi families were grandfathered in and it is now zoned single family.  Does anyone have any experience with re-zoning in a situation like this?   Is it even possible, or are there any other ways? 

Thanks in advance