I ran it in Sept 2011. On that Dream cruise there was no sign-up, you just showed up at the start, got a bib, and ran. On cruises after that I've noticed in the Navigator a sign-up location on the ship prior to the gangways opening. I've read where sometimes you get a bib, sometimes not. Sometimes you get a certificate of completion in your stateroom later during the day. Sometimes not. Sometimes of maybe it was in the past there was a commemorative water bottle left in your stateroom later. Sometimes not. Theres a plastic finishers medal sometimes but not all the time. Sometimes crew/cast run with the group. That didn't happen when I ran it. The 1 girl rode a bike & called finish times when you came to the finish. We got a bib that we could keep but that was all. Nothing more.
The course isn't particularly scenic. Not much to see, really. You start by the bike rental stand near Pelican Point, run past foliage out to the runway, then turn right into the bike path which is all brush with a few little artifacts randomly sitting off the edge of the pavement. When you do the bike loop you come back to the same point if the runway you entered the path at. You turn right and go all the way to the end of the runway where Serenity Bay is. Along the runway is brush and vegetation. Trams will pass you. Circle around the runway end, go back to the bike path, make the bike path circle a 2nd time, then back to where you started from. I'd say 95% of the scenery is pavement and brush. No shade. There's a few water cooler stations along the way.
In September when we ran it the heat was excruciating. Especially when you make the bike path loop, the closed in path (a little wider than a golf cart path) with the brush allows zero air movement. It was like running in an oven. The runway rivaled the bike path in that it felt like running on a frying pan. But at least you felt the air move a little. And if we fell over dead from the heat on the runway there were more people to come scrape you up fairly quickly. Lol! It'd be better if they ran the thing before the sun was up so high. The sun is brutal. We ran at about 9 or so. I'd say the heat was easily 90+ by then.
So, yeah, my youngest (then 14) & I ran the CC 5k once on our first cruise. Subsequent cruises I've used my CC time for leisure. I'd rather run deck 4 on the ship when its cooler, breezier, and there's scenery to enjoy. That's just me, tho.