Frank, I went to Lake Ediza a little more than a month ago. Spectacular scenery. The entire trail is well signed and very easy to follow. There are a couple of intersections where it would be good to have looked at a map (or better, bring a map) to help you choose the right turn, but once you cross the San Joaquin River (which strangely drains into the San Joaquin Valley from the east side of the Sierra), you're basically hiking up into a canyon/drainage, so you keep going west. Don't carry more than a half bottle of water at a time; accessible water sources all along the way (bonus!). If anyone didn't want to go all the way to Lake Ediza (7 miles), any point would be a good turnaround. Shadow Lake is about four miles and also beautiful. At the time I went, I didn't realize that the shuttle didn't start running for about another week and I wasted 20 minutes trying to find an open ticket window or someone to ask. It's actually quite obvious (when open); you park on the right side of the road at Mammoth Main Lodge and the ticket window is right there, close to the road. It's $7/person. The NPS website says something about accepting passes, but isn't specific. That road to the trailhead is almost all one lane and there's some trailhead parking, but not a ton. I'd have no qualms about using the shuttle. My understanding is that it runs frequently, and I'm not aware of any real complaints about it. (Almost forgot to mention: when you get to Ediza, the log bridge to the main camping area at the northwest side of the lake has been broken by another log falling across it, making for a sketchy crossing. At least, it was to me carrying a 35 lb pack.)
