The Duke and Duchess of Cambridge will arrive in Los Angeles on July 8. Their schedule calls for several days of travel and appointments around LA and other cities;
Both Secret Service and Department of State Bureau of Diplomatic Security have possible involvement in security operations for the Royal visit, but media reports have mentioned the DoS as being the agency for this trip.
If scanning the visit, be sure and keep an ear on local and CHP channels for activity, and search the UHF federal band (406-420 MHz) for State Department activity. And don't forget there will most likely be some British Royal security presence as well. The last time I ran into British VIP security in the US they were using some 160 MHz frequencies.
For a list of Secret Service channels, you can check my previous post,
Here is a quick list of possible Department of State Bureau of Diplomatic Security frequencies. They should be all P-25 digital and utilize a NAC of either N293 or N0F0. Be sure and let me know what you hear active: