Currently I do have a constraint for LA, DC, and NY. I guess I'll have to remove.
Yes, with the the current functionality and taking into account how your AD is organized, it ill be, probably, not possible to define a list of possible values and allow entering some free text at the same time. We have a suggestion in our TODO list to make it possible to enter free text when a property constraint is of the type One of the following values only, so that a drop-down list would be only a list of suggestions, allowing users to enter some free text if none of the values in the list match what they need. If this functionality would be available, this would solve the issue, so, we think, we'll just add a +1 to that suggestion.
I guess my concern is, we cannot have a custom command and give them the freedom of entering an address when need be.
Why not? The Custom Command would only set the address for those offices that are listed in the Custom Command. If a user types something that does not match any of the Conditions in the Custom Command, the Command will simply skip the user and will not clear the value entered by the HR for the address. For example, the following Custom Command will set an address for a user automatically only when NY, LA or DC is specified as the office. If the HR specifies something other than the above three offices, the Address will not be changed by the Custom Command.