I just spent a week in the Weminuche. Late, Aug. actually. My trip report might give you some idea what to expect.
http://www.14ers.com/php14ers/tripreport.php?trip=12786

Just a heads up, but Vestal's backside is actually pretty well cairned (almost to the point of ridiculousness) and easy to follow now. Most of it is class 2, but the class 3 options are more fun and solid anyways. The loosest part is gaining the saddle between Arrow and Vestal. The approach trail is also pretty good. Some deadfall but not bad at all.

I'm not sure when the trail/route was improved (sounds like the past couple years), but I was up there a couple weeks ago.

Kiefer Thomas wrote:Bit of advice on Vestal: the class-3 backside 'regular' route is hard to follow. It's poorly cairned as that entire south side is loose, a bit on the rotten side and crumbly.
Completely opposite from the North Face. Just take care and mark your path or note certain features (what I do).
Hiking up into Vestal Basin is a bit of a bear too. Lots of deadfall.
You're gonna fall in love with the San Juan's, buddy!