My guess is that you will hit snow around by 10,000' and maybe even lower on some of the north facing slopes. Getting to the top of Shepherd Pass is comparable to doing Mount Whitney; so Tyndall is harder than Whitney and Williamson is harder than both Tyndall and Whitney. Tyndall's North Rib might have some icy snow on it as well as short Class 3 section on Williamson. The slope to Shepherd Pass isn't that steep, but you may run into a cornice at the top. It might just be a partial one that you can get around though. I don't imagine that creek crossings will be a major issue this year.
Although the lower part of George Creek is pretty rough - you might look into that route for an early season Williamson climb.
Even better might be Split Mountain from Red Lake if you're looking to do a 14er.
Anyway, go out there and enjoy - just go as far as you're comfortable. You can always go back another time if you don't make it this time. There's nothing like the Sierra in the spring once the snow consolidates.
