Do both the Romulans and the Klingons have cloaking devices? I mean, for all their smarts, the Vulcans did not bother to cloak? What gives?
Yes, Romulans and Klingons both have cloaking technology.
The Treaty of Algeron between the Romulan Star Empire and The United Federation of Planets, in addition to establishing the neutral zone also prohibited the Federation from developing cloaking technology of their own. Of course they did anyway in super sekeret, as on the USS Pegasus.