@elbanditoroso
“I can sort of see why you wrote “Ventura Blvd.” because that seems to run right up to the foothills – is that correct?”
That’s close, although I’d say it runs approximately parallel to the baseline of the foothills.
“What about Glendale and Pasadena? Seems like those could be included in the valley, or not.”
I’d say the southwestern protrusion of Glendale is in the valley, and the southern protrusion is in the Cahuenga Pass, which connects the valley to the Los Angeles basin.
Pasadena is in the San Gabriel valley, which is separated from the San Fernando by the San Gabriel mountains.