Stopping for water during a 5k? C'mon, now! There's no need to stop for water during any race that lasts less than an hour. I might consider stopping for gatorade/fuel (but not water) during a half-marathon, but I haven't yet in the two that I've competed in. You should be well hydrated at the start and unless you race for longer than an hour (or maybe 45 minutes if it's very hot), you don't need water. If your urine is very pale yellow/clear before the start then you are hydrated and ready to roll.
I didn't stop for water in the first couple of 5Ks that I ran. I was too concerned about meeting my target time. On my most recent, I was well-ahead of my target, so I figured, why not? I ended up getting a cramp in my side almost immediately after, and found it difficult to get back to my pre-stop pace. I think they should have water available, but unless you feel like you absolutely NEED it (or as others said, you are running at a 30+ minute pace), I'd skip it and just keep running.
3/7/10: Seaside School Half Marathon & 5K -- 28:53
3/27/10: March for Misty 5k Fun Run -- 28:47
5/1/10: Fiesta of Five Flags 10k -- 1:01:46
6/5/10: Billy Bowlegs Night 5k -- 27:18
10/2/10: Epcot Wine & Dine Half Marathon -- 2:20:53