Rachel, welcome to WhitneyZone!

Fresno may be the most difficult place to use for a JMT hike.

There is the Yosemite YARTS that runs out of Merced, CA to Yosemite. And Amtrak runs through Merced (Fresno, too).

But look into the Eastern Sierra Transit Authority. They run the Hwy 395 from Reno, NV, through Lee Vining (with YARTS connections to Yosemite), Mammoth, Lone Pine (you can hitch to/from Whitney Portal), and Lancaster, CA.

From Lancaster, there are connections to LA.

So, you have options. Unfortunately, Fresno is not the best starting/ending city. If you use YARTS, check their schedule -- it may start to cut back in September.

Please keep us posted what works best for you, because others often ask similar questions.