According to The Huntington Beach Wave, the new entry signs for the City of Huntington Beach (now under design review) will be the first in over 100 years.
Here's a fairly common postcard image, showing an entry sign in the 1940s. There was also variant of this sign that read, "Huntington Beach - California's Finest Bathing Beach" that was standing as recently as 1952.
And can we count the giant neon "Huntington Beach" sign that hung from double arches at Main and Ocean (PCH) in the 1930s? No, it wasn't at the city's border, but you could read the thing from Long Beach on a clear night.
I also remember large horizontal wood signs with the classic Cold War-era "HB" logo on them. I know there was one on PCH on the northwest side of town, and I vaguely remember another one on Brookhurst St., near Garfield Ave.