I highly recommend it! I was a free skier that first went to ski school in my 40's. It was awesome. I too wondered about being a newbie. As already mentioned in this thread, everyone was very welcoming and I started meeting so many wonderful people in this water ski community. I too got addicted to skiing the course, but I still love my free skiing. I highly recommend @lpskier suggestions about physical preparation and pacing yourself.
I recommend finding a place that has a fun, low key vibe, where you can ski and learn, but also has room for you and your lake buddies to hang out between sets. It is your first ski school, and I think it is best to go with an mindset of low pressure, wanting to learn and try something new, not set expectations on performance, and instead enjoy getting to spend a week doing something you love and hanging out with friends. Nothing is better than a day skiing and hanging out by the lake with skiing friends. You surely will have some good stories to share on the dock. One will likely be, "Wow those buoys come fast"
I haven't been to many FL locations, but can recommend the @theboardingschool . I think they would be a great first ski school experience.