A week or so ago, I watched the movie Valley Girl. The movie came out in May 1983 and was filmed, according to imdb, in the fall of 1982. I find it interesting that it was released only nine months after Fast Times at Ridgemont High (from here on out, Fast Times or FTARH). FTAHR was filmed, again, according to imdb, in November and December of 1981 and like Valley Girl, Fast Times is also set in the San Fernando Valley.
The movies at a surface level seem similar – both are teen movies set in the same place and the same time, but in my view – the year between when the movies were filmed seems like the demarcation point between the 70s and 80s. FTARH, which is based off of a book written in 1979, has a late-70s vibe to it, especially with Spicoli and Damone. The music, except for maybe the go-gos, is also mostly late 70s. Valley Girl, otoh, is a full blown 80s movie and seems more like a John Hughes movie.
Now of course although both movies are set in the Valley, its certainly possible that the film was looking at different subgroups within the same region. It could very well be true that FTARH is set among the more working class parts of the Valley (like Damone lives in an apartment) while Valley Girl is set in the wealthier parts of the Valley. I know Adam Carolla in his book Not Taco Bell Material talks about growing up in North Hollywood around the same time and how similar it was to FTARH. North Hollywood, from what I know, is in the more middle class part of the Valley.
On the other hand, It should be noted though that Stacy (played by Jennifer Jason Leigh) and her brother brad (played by Judge Reinhold) and Stacy’s friend Linda (played by Phoebe Cates) seem to come from a privileged background and probably have more in common with the characters in Valley Girl. But none of them have the over-the-top preppiness and/or slang that the characters in Valley Girl have. But its very possible that the “Valley Girl” stereotype of the 80s was probably an exaggeration and that Stacy and Linda in Fast Times were probably a more accurate example.