*NOTHING* IN THIS POSTING CONSTITUTES LEGAL PROFESSIONAL OR TECHNICAL ADVICE. *NOTHING* IN THIS POSTING MAY BE TAKEN AS PURPORTING TO BE SUCH ADVICE.You're not the only one who likes to cover his butt ... Glad to see that you're aware of the need and are trying to ensure that your butt is covered.
OK I'm back - fed, rested, refreshed, and all those other desirable things.
I'll start by saying that there's a lot of material on your site and that you've obviously put a lot of thought, time, and effort into it.
I echo Abbeyvet's suggestions and comments about your color scheme and navigation. As the site is at present it *is* a bit unclear. You're so close that it'd be a shame to miss out by a fraction. 
Now the pop up:
Well it'll drive visitors away. Why not have a prominent welcome message instead offering people the chance to sign up for it. Try emphasisng that it's part of your efforts at building community amongst basketball enthusiasts etc etc.
The "agreement"
From the non-technical visitor's point of view clicking on "I disagree" does not *appear* to do anything.
In any case "to agree" "to accept" and "to consent" have very different meanings both in dictionaries and in many courtrooms.
I wonder whether clicking on "I agree" constitutes a valid acceptance. You *don't* tell your visitors what they are agreeing to.
That's why "adult" sites (to take the most glaring example) specify what it is you're agreeing to.
Perhaps you should rethink....
Many bar associations offer cheap advice schemes whereby for a small fee you get a ½ hour consultation with a local lawyer.
I hope this helps.