PHOENIX - City officials have launched a bilingual marketing campaign that they hope will entice Hispanics to participate in a mid-decade census that could save millions in state and federal funding. The Census Bureau surveys the nation's residents every 10 years, but cities can update population figures after five years. Maricopa County cities will mail surveys this fall to adjust the 2000 counts. Updating the count in cities with large minority populations is critical because minorities are historically undercounted. An undercount can cost municipalities millions for programs such as Medicaid and foster care, which are funded based on the census numbers. The census also reallocates congressional seats based on population changes. Hispanics, especially illegal immigrants, have long been undercounted because of language barriers and the fear that their personal data will be shared with immigration officials. In Phoenix, about 37 percent of the city's 1.4 million residents are Hispanic, many of whom are undocumented. About 27,000 of Phoenix's 600,000 households will be surveyed. The city is paying $1 million for the bilingual mail-in survey, which goes out Aug. 29. It will include a bilingual letter from Mayor Phil Gordon urging residents to participate. The city is also working with Spanish-language television and radio stations to get the word out, said Norris Nordvold, the city's intergovernmental affairs coordinator. Officials already project Phoenix likely will lose up to $25 million in revenues beginning in July 2006 because growth has slowed. "But if a lot of our folks don't return the survey, then we'll lose much more, because we'll have to go door to door, and that is always very costly," he said