It's two years since Boston Chicken soared 143% the day of its IPO. Now comes Rainforest Cafe, a jungle-theme restaurant in Bloomington, Minn. On Apr. 7, it floated 38% of its 4.6 million shares at $5. They've since topped $15, giving Rainforest an indicated market value of $65 million. Not bad for a company that should post sales of only $9 million this year. Investors bet the eatery's wild decor-live parrots and talking banyan trees-can be cloned: Six more are due to open by late 1996.