I would be the most concerned about the rear tire and having a flat back there, that one is the most likely to have a flat and will take more time to repair it due to the mechanicals. So at the very least I would get a better tire than what you have back there and install liners in it and on the front tire you currently have. You won't be out that much money for one tire and two liners and it will save you headache on that ride. Make sure your bike is in tip top shape before you go.
Make sure you carry some food with you, yes I know there are SAG stops that supposedly have that stuff but the last time I did it, which was many years ago, the SAG support was lacking, a couple of the stops didn't have any food at all and one had no water. Volunteers use to be in short supply so we just helped ourselves to whatever was there, so just to be safe carry more food and drink then you think you'll need. More modern times has seen an increase in the popularity of such rides but just to be safe I would carry enough food in case one stop has nothing, and use those SAG stops first for food and water before going after your supply. Carry some cash on the ride just in case.
The event use to be poorly organized so be mindful of that too, cops won't be at every intersection especially once the middle of the pack has gone through, so watch your intersections. And get back before dark obviously because you won't have lighting and they start removing all the stuff associated with the event. The scenery there will be very nice, the weather will be nice once you warm up, usually in the 70's but could be colder in the morning and will get colder as evening approaches so wear some sort of jacket that you can pack away. Wind can sometimes be an issue too, so depending on what the forecast is you may want to take a windbreak vest.
Usually the sunshine is pretty high so you may want to use sunscreen, and helmets are a requirement.
If you know anyone who has done it recently ask them about what to expect and then prepare for the worst just in case the SAG and volunteer support is subpar this year. If you'll be spending the night in a hotel make sure you get reservations NOW! if you wait till a couple of weeks before the event you'll be sleeping on a park bench!
I use to have a vacation condo I owned and rented out there in Palm Springs so I'm sorted of acquainted with the area and that ride but I still had to get a motel, why? because it was always rented out in the fall, winter, and spring!