Welcome to the Springs. Talk to Cecil, the rec director over at the Academy. Also, plenty of people from town post on here. Or, you can try our local club forum, which is in my signature. The season and runs really depend on where the snow is and when it's melting, or when/where there is rain.
The season starts when you want it to, depending on how much you link mank and cold weather. I usually start boating in February or March, and boat into September, maybe October. It just depends when I start getting sick of driving and what is running. I know plenty of people who may slow down, but pretty much never stop boating unless everything is frozen over.
As far a local stores, unfortunately there is only one that sells kayaks, and they only stock it in season. That would be Christy Sports over by Academy & Constitution. I don't recommend it though for meeting people. Really, Mountain Buzz or our local forum are much better for finding people to show you down runs.