I'm on the other end of the spectrum so, believe it or not, I have a hard time relating to a 5'8" model.
One point about buying bike shorts. Look for ones that have 8 panels. The fit is better and more attractive than a 4 or 6 panel short. They are in the higher price range and often have better chamois. Once you know which brand fits you the best it's easy to find them on sale.
I know it's hard to find your size in LBS's so you may need to order several brands online and then return the ones that don't fit. Just like buying bras online.