A food safety watchdog group has just released a report that should help diners choose restaurants that won't make them sick when they go out to eat.

The report, dubbed "Dirty Dining," was published by the Center for Science in the Public Interest.

It's based on restaurant inspections in 20 cities - including Seattle.

The report ofund that in one out of every four inspections, the restaurant was written up for contaminated surfaces.

In addition, 22 percent kept food at unsafe temperatures, and 13 percent showed signs of rodents or insects.

"You know, rats and roaches are kind of obvious evidence that there's some sort of problem and consumers should take that into account, but the problem that we see is that, what's invisible to the naked eyes is often what's more dangerous to the human body," said Sarah Klein, who co-authored the report.

She believes if the information was easy for people to use, food inspection reports would have a much greater impact on safety.

Klein points to Los Angeles County, where the restaurants are required to post a food safety grade - A, B or C - in their front windows. Las Vegas and St. Louis have a similar system.

"So we would like to see a very easy A-B-C letter grade system in the window that consumers can, at a glance, while they're making a decision where to dine, take into account," Klein said, "so that food safety is part of that decision, instead of just whether it has a Zagat guide rating and what kinds of credit cards it takes."

This system has been up and running in Los Angeles for more than 10 years now, and Klein says it has dramatically reduced serious cases of food poisoning there.

The study found that when it came to restaurant inspections, the Seattle area had some of the best scores. But what about the idea of restaurants around here putting food safety letter grades in the window?

The Washington State Restaurant Association does not support the idea.

An association spokesman said these inspections "are just a snapshot in time" and therefore don't give people a true picture of what's going on in the kitchen.

The restaurant association does support having inspection records online - something that is done here in King County.

Beyond that, experts say, diners should always make sure the food is the right temperature - hot food should be hot and cold food should be cold.

Another good tip-off is to check the restrooms. If they don't have hot water and soap, or if they're not clean, diners might want to think twice about eating there.

To view the full report, click here.