Jill,
We have a visitor's station in the lobby of our Medical Arts Pavilion, which houses mostly physician's offices. For us, the needs assessment was a plea and recommendation from the hospital's Outpatient Rehab staff. Their department is located on the first floor as people come into the building. Several times per day, people would go into their reception area asking for directions. The staff would have to take time to assist them, which often required getting up to direct them to different areas. Once we placed volunteers at in the lobby, this helped tremendously.
We only have a volunteer at the station in the mornings since most of the people have morning appointments. I think you would have to find a way to show the need. Is it possible to post a volunteer in that area for a week to tally how many "assists" they make? Or, maybe you can develop a short survey and distribute to the physicans' office staff to ask if their patients have made any comments about finding their office. Hope this helps.