I have been up the Palm Springs Tramway, and they have some trails that are designed for wheelchairs, but end not too far away from the Main Upper station. so that is one option. Note it will be cold, and maybe some snow at the top of Mt. San Jacinto. Here is a link to a live web cam at the top of the mountain next to the Mountain Station.
The Living Desert has many of its trails paved for easy use by Wheelchairs.
>>Accessibility: •Paved pathways throughout The Living Desert make exploring accessible for strollers and wheelchairs.
•Adult wheeled strollers and Zebra-themed children's strollers are available for a $3.00 donation.
•Explore The Living Desert on a Shuttle.<<
And there are many more options, but these are two of the more popular ones.