The recent craze for converting apartment buildings to condominiums, which is drawing political heat in Los Angeles and elsewhere, may be slowed by market forces before City Hall has a chance to act. One possible indication of a coming slump was the number of people willing to pay $1,800 for investment advice on the topic. Only about 50 signed up for a two-day West Coast Condo Conversion Conference, sponsored by the New York-based Information Management Network and held at the Hyatt Regency Century Plaza. "Even six months ago, this room would have been packed," said Delores Conway, director of the Casden Forecast at the USC Lusk Center for Real Estate, as she glanced around at dozens of empty chairs in the chilly auditorium. With interest rates up, real estate prices stagnating and many new condo units coming on the market, the easy money possible for conversions two years ago is a thing of the past, Conway said. "The whole market has slowed down. The speculators are gone," she said. "I think condo conversions are always the last part of the cycle."