A lot depends on whether you have a directional antenna.
First of all, best time of day (except where noted below) would be the middle of night, though nailing down an ID is more difficult then because so many stations run syndicated or network programming overnights.
KFI-640 in Los Angeles may be your best bet. Looking at the NRC Pattern Book, I'd say the following California stations that I regularly hear here in Edmonton are also worth trying:
- KFBK-1530 in Sacramento looks possible, though you may have "null out" (position the antenna or radio if it has an internal antenna) WCKY in Cincinnati.
- KNX-1070 in Los Angeles, if you can null out the smaller stations in the U.S. Midwest
- KTRB-860 in San Francisco would be quite tricky. You have have to catch them on Day Pattern, before sunset their time, but after sunset in Saskatoon, when CBKF-2 switches to a Night Pattern that sends very little signal in your direction. And there is still CJBC-860 to worry about, though they should null out nicely with a directional antenna