I was in the Ruth for the first two weeks of May. The weather sucked, only 3 days it did not snow. I used a 15 degree bag and was plenty warm. The coldest it got was 19 degrees on top of Mt Barille (open bivi). Remember, you will be camped at around 5,000 feet so it will be considerably warmer than Denali.
Fly with Talkeetna Air Taxi, they will fly you anywhere in the gorge, whereas the other flight services will only drop you off at the Mountain House. Expect to pay 350.00 or so.
For easier routes consider Japenese Couloir on Mt Barille, Mt Dan Beard, and West Face of Mt Dickey. Stepping it up a notch SW Ridge of Peak 11,300 and Ham and Eggs on Mooses Tooth. Also, you may want to PM joepuryear. He is good source for a lot of information.