Thats correct, it's a 16 min. mile pace - i wouldn't assume they will let you go much past that though, as to clear out the streets and open up parks - They have to shut down some major roads for the race, so they can't give you all day to finish.. LOL
I personally didn't see people get swept -- but i had about 1,000 people behind me, so i really wasn't worried about it either. We DID see the sweeper buses though - in a couple locations.
If you train now, and stay active, then seriously train for the 14 weeks or so before the race, you will be FINE!! I started training following the MfM book plan, and it's 14 weeks - (before that i was doing 2-3 days a week of say 2-3 mi.) and it worked great - my time was about 3:15 for the race - so we were under the time limit - this year i would be thrilled to do 3:00 hours - i am staying with my mom, so i am not going for a crazy fast time - as i don't want her over-doing it either.. It's honestly not about the time, but more about the fun for me..
It really is a blast -- as hard as it is, it is extremely fun at the same time! LOL