Fortunately, we've never had a problem, which I attribute to more luck than planning and preparation, but here's a few observations that I hope will help you cope (and avoid sickness).
1) CS condiments bars. A few places have 'em, and although I've been lucky, I will avoid these places like the (norovirus) plague. They are generally kept clean, but during peak periods, the cast members are too busy bussing tables and serving meals to wipe-down and sanitize. As the CDC fact paper states (
http://www.cdc.gov/Ncidod/dvrd/revb/gastro/norovirus-qa.htm), it only takes a few noroviruses to infect. This isn't the Disney Wonder, so there's nobody handing out sanitizing hand wipes before you get in line. Besides, the open tomato/onion/relish bins get to look pretty unappetizing after just a few minutes, and the mess that serves as a condiments bar at the Pirate and Parrot can make you physically ill just looking at it.
2) Restrooms. Again, people go there to... ahem ... rid themselves of bodily fluids and waste matter, which are vectors for shedding the norovirus. I'd suggest washing hands going in, and again coming out. Try not to touch the push plate or door handle with bare hands -- use a paper towel and/or your feet to open the door. And, no, I don't suggest pulling the door open with your feet, unless you have no hands (which I have actually seen, and I applaud that person for having the wherewithal to tackle an otherwise unfriendly environment). But then I'd want to wash my foot as well.
3) Resort/Park All-Day Mugs. These are great values -- these are also EXCELLENT vectors for harboring/spreading norovirus. How many of you thoroughly wash the mugs with soap and hot water between uses? I hope the answer is ALL OF US. I'll bet, however, it isn't.
4) The bologna-sandwich-in-the-backpack. Raise your hand if you've NEVER sneaked food into the park...ok, now raise your hand if you've never lied about sneaking food into the park. Anyway, how long did that sandwich sit before you ate it? Was it still cold when you bit into it? Did you happen to get ill later that day? Look up "food poisoning" on the Internet and compare those symptoms to what happened to you...
5) Look at what you're eating. It happens all the time -- you order a burger, with tomato, lettuce, cheese and pickles -- and when your food arrives, you just wolf it down. But even the best places will occasionally make a mistake, and maybe the food-service cast member didn't notice that rotten spot in the tomato, or that blue fuzz on the edge of the cheese slice. Maybe they couldn't smell that off-odor from the guacamole. But you owe it to yourself to take a closer look at the food that you get from mass-production food service. And if it doesn't look/smell/taste right, take it back and ask for a replacement. (And be sure to take a double-hard look at the replacement food -- food service workers have been known to resent customers who send food back!)
OK, that's just my 2 cents (more like 20 cents) worth. You can go and enjoy without being paranoid. But it never hurts to be prepared -- pack chewable Pepto-bismol tablets, and immodium, just in case. Yeah, there's argument about whether or not you should stop yourself up with immodium, or just let nature take its course. To my mind, immodium is better than causing a biospill of the worst kind on Mission:Space. You can unplug when you get home.
Regards!
(1/22-1/28) and no viruses for us! 
