Dedham residents are most concerned about illegal drugs, school safety, alcohol abuse, break-ins, and property theft, according to a police survey released last week. Of the 517 who responded to the survey, about 68 percent listed that they were “concerned” or “very concerned” with illegal drugs and with school safety, the highest total of the 21 crimes listed. More than half of respondents said Dedham has about the same crime rate as other neighboring towns, but 38 percent said they thought there was more crime in Dedham. Only 9 percent said they thought there was less. About 55 percent of residents thought crime had increased in the past year, with 4 percent thinking it had decreased.