Since you're staying in Lower Pines, your campground will be crowded mornings and evenings since the campsites are pretty much right up against one another in the Lower Pines campground. (Just giving you a heads-up.)
If you hate crowds, avoid all these trails between the hours of
9:00 AM and 6:00 PM:
The John Muir Trail (from Happy Isle)
The Mist Trail
The trail (road) to Mirror Lake
The Lower Yosemite Falls Trail
The Upper Yosemite Falls TrailTrails that during the day won't be that crowded (though there definitely will be other people on the trails):
The Valley Loop Trail (west of Yosemite Lodge and Swinging Bridge)
The Four Mile Trail.
The Pohono Trail
The trails to Sentinel Rock and Taft Point.
The Panorama Trail (though it ends at the junction with the John Muir Trail which will probably be crowded).There are also a couple of old abandoned roads (the
Old Big Oak Flat Road, and the
Old Wawona Road) you are allowed to hike on from the valley floor that won't have too many people on them either.
Also, remember that you're free to travel off trail (unless an area has been posted off-limits by signs) in Yosemite, including Yosemite Valley. Just parking in the western half of Yosemite Valley at a designated paved pullout and walking no more than 100 feet will take you away from 99% of all the park visitors.
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