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;
http://www.kcoy.com/story/14924375/schedule-released-for-royal-visit-to-california
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,
http://mt-fedfiles.blogspot.com/2008/02/secret-service-frequency-list.html
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:
406.3750
407.2000
407.5000
407.6000
407.8625
408.1000
408.4000
408.6000
409.1500
409.5250
409.6000
409.6250
409.7000
411.0750
411.1500
411.4250
412.0000
412.2875
415.9000
416.2000
416.2250
417.6000
417.8500
418.0500
418.0750
418.4500
418.5250
418.5750
419.3000