First, not all jean shorts are created equal, especially when you are shopping at the thrift store. In fact, most are hideous and wrong in many obvious ways. I looked at lots of pictures, and what I don't want is what every girl at Coachella seems to be wearing - skimpy, shredded, pocket-bag-showing. I want a fairly high waist, not too tight, with a finished hem. The pictures below illustrate some styles worth considering.
The pictures below also illustrate the second dilemma. Legs. It's pretty hard to judge a jean short as seen on a super long, lean, tanned leg. For one thing, my thigh is not three feet long, making the length of the short much closer to my knee than my crotch, which is a good thing. But there is the issue of whiteness. Which I embrace, as I have no real choice, but I think I'd have better luck trying on shorts if I wore tights, at least until I get a little bit of sun.