Was I remembering right that Israel is huge on watermelons? A quick google shows that even today (not just my childhood) the answer is a huge yes:

  1. Haaretz: The seedy side of Israel's beloved watermelon "There's nothing like cold watermelon in the summer, especially during a painful summer like this one. But why is this iconic treat so pricey?"
    Nighttime in Tel Aviv. Unspeakable mugginess at the pool on the roof of the Marina Hotel, feet immersed in water, elevator music in the background. I'm torn between two items on the menu: watermelon soup for 38 shekels ($11), and watermelon with salted cheese for 32 shekels ($9.25). The waitress informs me they're out of soup.

    "Avatiach adom" (translation: red watermelon)
    matok (sweet)
    bli-gar'in (without seed)" here
  2. While a column in the Jerusalem Post (trying to defend Israel's "democracy" status, which I'm not sure if I agree..) states that, get this: "Rather than being a banana republic, Israel is a 'watermelon democracy'" with lines like this in the article:
    Just as watermelons have hardy structures and tough rinds, we don't easily change basic governing arrangements like president as head of state, prime minister as head of government.

    Watermelons, like democracies, are delicious inside but delicate -- consent of the governed, rule of law, civil society and civil liberties are sweet gifts. But these arrangements are fragile and can be ruined through corruption, demagoguery, dictatorial power, lack of faith -- pits (or pips) which must be spit out for the experience to be succulent.

  3. While the Times of Israel runs articles with headlines like: Watermelon brings Jews, Arabs together in shadow of Old City walls (first photo caption: "Jews and Arabs share a plate of watermelon", later photo caption, "Benayun, Israeli and Ohayon working the watermelon stand")

In contrast I found next to nothing as far as summertime roadside fruit stands (which were definitely mostly watermelons) of my childhood memories, so that part (rickety wooden structures for roadside stands) may have changed the most.

But as the above quick google finds suggest, as for watermelons being huge in Israel? Most certainly!

Postscript, actually, I did find one direct confirmation of 1970s having roadside watermelon stands:

Kind of disturbingly gun-filled background of watermelon stand, titled "Micha Bar Am. ISRAEL 1974. Tel Aviv, a watermelon vendor along Hashalom road" (pinterest original) Ironic since "Hashalom" means "the peace"

Though I would think that there are still some roadside fruit-stands (mostly watermelons, some melons, and less often sabra (cactus) fruit back then, probably not a radically different mix today), just fewer of them....and also, the roadside stands I remember from childhood did not have such gun-filled (or few if any other type of such mural style art) in the background, I'm glad to say...

how Yemenite Jews dress and their appearance also here