French people do say oh là là, hou là là and houlà quite often but it doesn’t have the connotations found in English. Well, it can but rarely.
Here are examples of its use in French:
Il est déjà sept heures. Hou là là, je vais rater mon train !
Oh là là, elle a repris du gateau !
Hou là là, il a du se faire mal en tombant !
A reason explaining the popularity and oriented meaning of this expression in English might be Fifi D’Orsay, actress and singer born in Montreal who made all her career in the US and who made hoo-la-la her trademark according to several sources.
I got the idea from Agatha Christie’s books featuring a character of belgian origin by the name Hercule Poirot who often inserted French words into his otherwise English dialogue, such as ‘alors’, ‘monsieur/madame/madmoseille’ and also ‘Oh, la, la’:
“My dear Poirot! What on earth is the good of that, now that we know
about the coco?” “Oh, là là! That miserable coco!” cried Poirot
flippantly. ~Agatha Christie – The Mysterious Affair at Styles
While I realized that Poirot with his enormous moustache and mannerisms was a caricature of a Frenchman, I still remember this phase as a french expression.