We moved to Phoenix about 7 years ago from the mountains of Arizona and we LOVE GOING TO THE RIVER!! We will get a big group together and go a few times every summer (going on July 6th next actually). I can't believe the last review from out of town visitors.... You are tubing down a river that has rocks, rapids, etc... Duh there are always risks involved but you need to be smart and aware.
We actually bring our own tubes and have another vehicle go and park at the end of the river, cheaper and better than using the salt river tubes and buses. Make sure to get a Tonto pass thought (only $6 from the gas station). Bring LOTS OF WATER, beer, food, water shoes (so you don't hurt your feet) and sunscreen! We always have a great time. Warning... there are always idiots out there though, I mean rude people and people that are way too drunk. There are some ghetto people that hang out under the bridge (point 2) that like to shoot water at you and try to annoy you when you go by just an FYI. We like to go from point 1, which is usually about a 4 hour float trip, if the water is running right but the last time we went was Memorial weekend and point 1 was running at about 6-8 hours, so make sure you check before you take off.
I think everyone should do a float trip at least once, it is absolutely beautiful out there and a little fun adventure. The end is kinda a pain in the [--] because you have to drag all your stuff up after you get done but all and all it is worth is. Since AZ doesn't have a beach we have to make the most of our summers here. Also if you want to mingle with people you should stop at the cliffs, it is where most people stop to hang and some jump off the cliffs, which I don't suggest at all. Enjoy yourself though, be safe and smart but have a good time :)