Michael,
This is an interesting question and interesting search. Is your colleague heading to the Esri UC in San Diego later this month? That would be a good start to find San Diego-based GIS users in Public Safety. Other than heading to user group meetings (especially local ones in those cities/areas), I feel that it would be hard to find these specific groups of people. The GeoNet is a good place to ask though.
Maybe you could find local contacts to local GIS user groups in San Diego, NYC, and Baltimore and reach out from there. I only presume cities as big as these would have 'local' user groups.
There are very few user group communities on the GeoNet. Tagging: San Diego County Regional GIS Users Group and DC GIS
This looks to be a website of an NYC GIS group:
GISMO….a GIS hotspot – a GIS hotspot
Here is potentially another one: http://www.meetup.com/geonyc/
This might be your best bet for San Diego:
San Diego Regional GIS Council
And for Baltimore, this should work:
Baltimore Region GIS Committee - Baltimore Metropolitan Council
