Take this with a grain of salt, because it’s a survey of early adopters who were already planning to buy a smartphone. But when they were asked what kind of device they hoped to purchase in the next 90 days, 21% said they wanted one powered by Google’s (GOOG) Android operating system. That’s “a monstrous 15-pt jump” since a similar survey three months ago, according to a report released Monday by ChangeWave Research.

And although Research in Motion (RIMM), with 39%, and Apple (AAPL) with 31%, still dominate the installed base among ChangeWave’s plugged-in membership, Google’s Android is growing faster. Four percent of those members now own Android phones, up from 1% in September.

Meanwhile, interest in buying iPhones fell four points over past three months, from 32% to 28%.

“To put this in context,” write ChangeWave’s Paul Carton and Jean Crumrine, “three months ago Android OS was tied for last place in consumer preference among the major mobile operating systems. But since then it has surged into second place ahead of all competitors except the iPhone OS X (28%) – which remains the number one choice.”

Interest in buying Palm (PALM) and Microsoft (MSFT) devices continues to shrink, as evidenced by the chart below the fold.

The survey was conducted between Dec. 9 and 14 among 4,068 consumers drawn, according the ChangeWave Alliance website, from “a worldwide group of 25,000 highly qualified business, technology, and medical professionals … who spend their everyday lives working on the frontline of technological change.” For the full report, click here.

[Follow Philip Elmer-DeWitt on Twitter @philiped]