Normally in I would not bring jeans to FL in warm months, but last summer we happened to have some and hit a cool evening in AUGUST! I was glad to have long pants. I've also hit cool weather in early November several times. In winter, we happily wear jeans in WDW. So until you know exactly what the weather will be, it's impossible to say if you will feel comfortable wearing them - temp wise. Personal preference plays a big role.
Drawbacks of jeans at WDW are: wetness, pocket space, and laundry.
Water rides + denim (even shorts) = miserable. Skip Kali/Spash- or wear something different. WDW has lockers, but a bit of a pain. Wearing plastic ponchos on water rides is for whimps. Odds are also good you'll have a rainy day. Wet is wet. On a rainy day, easy dry fabrics are best.
More than once, I've lost things from jeans pockets at WDW. Zippered pockets are great at WDW. Cargo shorts, go without, maybe a stroller, a small cross-body bag are options. Each has pros and cons.
Last, this is a minor point, but basically you can't hand wash jeans/air dry them very easily. You can wear them more than once. Depending on lots of variables- sometimes it's great to bring a dress/shirt/shorts that can be hand washed and air-dried easily in a hotel room. Not essential, just sometimes helpful.