I've never had a problem with bike shorts riding up. Now baggies - whole nother story. Once again there wasn't an option when I first started riding bikes, I bought mens shorts. I'm interested in trying the shorty shorts but I usually just roll my shorts up a few turns and achieve the same thing. Since I don't swim, tan lines aren't really something I think about anyway.
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"