I'm pretty sure East Avenue was the east side of that road, but Interregional was the name of the west side. The IH-35 feeder roads retained these names for years, maybe they still do.
In the original couple of pictures, you can see, just south and east of the auditorium, the old National Guard Armory building that was probably a skating rink at the time, or the skating rink was the building just next door to the armory (the armory has the large billboard on top). The armory, of course would soon become the Armadillo World Headquarters.
The New Orleans Club was the place to see Roky and the 13th Floor Elevators, went there many a time.
I saw a couple of minor league games at the old Disch Field. Then you could go to an open air place on the corner of Barton Springs Road and Lamar for slices of watermelon.
And there was a playland park with rides across Lamar, where KFC is now.