I think I saw a comment here on HN from a Tempe resident that said that it's 45 in the direction the Uber car was going, but 35 the other way, hence the confusion.
edit Now it makes sense.
I went through Google Street View. Northbound on Mill Ave, from before Curry Road to afterward, is 45mph. https://www.google.com/maps/@33.4350531,-111.941492,3a,75y,3...
Southbound on Mill Ave, and on Center Parkway, there are no southbound speed limit signs posted. But after the Curry Road intersection, there is a 35mph sign. https://www.google.com/maps/@33.4371031,-111.9433154,3a,75y,...
I thought the Uber was north of Curry Road going south, but after comparing the video to the map, it looks like the Uber was south, heading north to the intersection. The road opens up and there are two metal signs. https://www.google.com/maps/@33.4362927,-111.9424451,3a,75y,...
So, yes, the speed limit on the road in the direction the Uber was traveling on the stretch of road it was traveling was indeed 45mph.
Also, very sadly, at the point of impact, there was actually a sign that said "Do not cross; Use Crosswalk ->". https://www.google.com/maps/@33.4365489,-111.942659,3a,22.9y... Although not facing the direction the bicyclist was crossing from. I'm willing to bet an accident had happened here before.
Really? This is really common. Think about a road connecting a town and a rural area. In the half-mile adjacent to the town, the into-town direction will be limited lower to get drivers to slow down as they approach town, and the out-of-town direction will be posted at the higher rural limit.