Yesterday, I took Temescal Canyon Rd from Lake Elsinore to Corona, to avoid some bogged traffic on I-15. When I got into Corona, I started seeing nice new Historic Route 71 signs. After poking around in GSV, I found that the signs are fairly sparse, but there is a respectable number of them. Since we have Historic Route 49 signs in a couple of towns, perhaps this should be added too.
Also worth noting: The signpost entering from the west also lists Historic Route 18 and Historic US Route 91. The signpost entering the city limits from the east lists those two but of course not 71. I don't know if it's appropriate to add Historic Route 91 just because of two signs in one city, though.