April is an awesome time to be in Yosemite Valley. Not too hot, not too many crowds and not too many mosquitoes. Getting from there to the east side, however, is a bit of a chore. If you have a month, though, I would definitely consider spending a week in the Valley.
For routes on the east side, depending of course on snow conditions and temps you could try the classics on Temple Crag, Incredible Hulk and several classics in the Whitney cirque. Might still be pretty cold but you might get a good window. Bear creek spire and the rock creek region has great climbing and skiing.
I haven't been into Langley but there are supposed to be some great routes in the 10's as well as good skiing...Again, might be a bit cold for a 14'er.
For skiing, you have plenty of time to do a trans sierra, sierra high route, evolution loop, palisades loop, sawtooth loop...Probably not all of those but definitely some great options.
Guidebooks:
http://www.amazon.com/Backcountry-Skiing-Californias-Eastern-Sierra/dp/0979264464/ref=pd_sim_b_4
http://www.amazon.com/Backcountry-Skiing-Californias-High-Sierra/dp/1560449136/ref=pd_bxgy_b_img_b
http://www.amazon.com/Classic-Backcountry-Snowboard-Summits-California/dp/0898866561
http://www.amazon.com/Climbing-Californias-High-Sierra-2nd/dp/0762710853/ref=sr_1_7?s=books&ie=UTF8&qid=1294962925&sr=1-7
http://www.amazon.com/High-Sierra-Climbing-Californias-Country/dp/0967239184/ref=sr_1_15?s=books&ie=UTF8&qid=1294962925&sr=1-15
and the sierra bible:
http://www.amazon.com/High-Sierra-Peaks-Passes-Trails/dp/0898869714/ref=sr_1_1?s=books&ie=UTF8&qid=1294963062&sr=1-1