The Li'l Jumpin' Bean was kit number G-8, and was preceded by the Swordsman 18 (G-3), Stuntman 23 (G-6) and the Spaceman 30 (G-7). As often the case, the plans do not show a date, possibly because they didn't want their kits to seem outdated? Who knew we'd be building them 60+ years later, with no regard for "state of the art?"
I love the style of all of the Goldberg plans. The isometrics showing how to proceed. The Brodak reproduction retained the Goldberg plan, but changed some of the engineering. In particular, they provided a nylon engine mount. A very fine mount, but I think for a Bean, I'd do it just like the original, just because.
AHC advertised the Stuntman 23 in September of 1960 (and possibly earlier), but not the Bean--yet. In May of 1959 for example, AHC was advertising the Swordsman 18 and the 1/2A Blazer, but not yet the Bean. But by early 1961, AHC was selling the Bean for $1.49 or you could get a Little Toot for $1.69. So Ken's answer is probably within 12 months of the first introduction.
I recall reading a chronology as given by Goldberg himself, going thru the logic of each and the tentative and somewhat unexpected growth of his venture. Wish I could find that again.