In New York, the big focus is on Chinese buyers.
Brokers say the wealthy Chinese represent about 10 percent of the market. But some of the newer luxury towers are aimed squarely at rich Chinese buyers. One57, the residential skyscraper overlooking Central Park, has signed up several Chinese buyers. And 56 Leonard St, a downtown luxury tower, has also been popular with the Chinese.
Nikki Field, senior global real estate advisor with Sotheby's International Realty in New York, said Chinese buyers are still out in force. If anything, she said, the slowdown in China and turmoil in Asian markets could bring in more Chinese buyers into safer havens.
"They want to move a lot of money out as quickly as possible and get it somewhere safe," Field said. "Residential real estate here is safer than other options."
Still, other brokers say Chinese buyers have started dragging out their purchases over several months or even a year. And some newer developments are seeing delayed payments from Chinese buyers.
Field said Chinese buyers like newer apartment towers, and "many of them don't come on line for another two or three years." So if there is a slowdown, it may take another year or two to show up in the market.
"Of course, the last 48 hours brings us some concerns," Field said. Chinese stock markets have been volatile amid concerns about tighter credit, which would slow economic growth.
"But the people buying real estate here are not using their last $5 million. These are people who already have the extra funds offshore and are diversifying their portfolio."
—By CNBC's Robert Frank. Follow him on Twitter