Carla, we had the same April Yosemite experience a few years ago!
we have almost the same pics. it was 73 degrees and sunny the first couple of days and then a cold storm blew during the night, dropping 3" of snow in the Valley.
as to what you can leave out, the bears are used to anything looking like a cooler, as possible food. even a water jug.
and don't leave anything outside, like grills, stoves, containers, that could have had food on/in it.
agree about even April getting booked up quickly.
__________________
Dan-Retired California Firefighter/EMT
Shawn-Musician/Entrepreneur/Wine Expert
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity