If you are in Phoenix's east valley Saguaro Lake is the closest to get to. It's the first lake just above the dam for the Salt River. As such you pass by the Salt River to get to it. If you plan to attend during warmer months on a weekend or holiday plan to see a lot of river traffic and buses.
As far as boating goes this is a great choice if you are wanting to get to a lake fast and there aren't many hills and curves in the road leading up to the lake. (Which is great if you have kids that get car sick ;-). Because it is so close I feel like it's the busiest lake. However, if you have early risers and can get there in the morning it's not so bad. There are a few areas that are good to stop and let the kids jump out and go for a little swim. From the land beach space is limited. Overall it's a great lake for a quick trip, if you have a boat.
***Don't forget your Tonto National Forest Pass! You must have this pass displayed in your windshield to park. $6 for a car plus $4 if you have a water craft. You have to get your pass ahead of time at a participating circle K, Big 5 and sometimes grocery stores have them. Try this link for a list of participating sites http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5331614.pdf