Generally, if its an arena they will be VERY strict. I remember once before a Heat game spending about 45 minutes trying to convince that my 17-55 didn't have any more reach than an 18-55. But they simply kept pointing to their picture of a Rebel with an 18-55 on it and saying No. Save yourself the trouble. If it says 3.5" then thats your limit, and lately some venues have been stressing a "single lens" rule.
The NBA has made it a league policy.
NFL, MLB, MLS, and the NHL are much more lax in their restrictions. But a good rule of thumb is bring a print out of what they say on their website with you and a tape measure if you wanna be cute.
Another tip: leave the vertical grip at home. You can spend 20minutes convincing its just a battery grip and not a power winder to no avail. I spend 15 one day at a Panthers game showing to an old woman (how they think an old woman should be in "security" is beyond me) that my grip on my 40D was a Battery Grip... 10 of those minutes pointing to the label right on the front that says BG-E2N Battery Grip. I of course got it in... but it took patience, perseverence and debating ability to make it happen.