OK, he's the only ice cream man in Seward Park. But that's the point. Seward Park is like a Parisian boulevard (with an old-growth forest). Almost every day of the week, everybody and their extended family comes out for a stroll, a bike ride, a picnic, or a hike to the tallest tree in the city limits. Refreshments are needed, and that's where Alex Isadore comes in. For 15 years, "every day the sun is out," Isadore has parked his ice cream truck midway between the playground and the beach. "I just love what I do," says the 54-year-old, who sports a shaved head, a beard, and a tangle of gold medallions. Money or not, he says, "I've never let a kid walk away from a truck without ice cream. You know what? Ninety-five percent of [their parents] come back and pay me." It helps that a soft-serve cone is only two bucks. You can get vanilla or chocolate?or his latest, "the Obama," chocolate and vanilla swirled together. Little-known fact: Isadore also offers hot dogs, also only $2 each. So you can bike around the park's 2.5-mile lakeside loop, eat lunch, then go for another spin. Eat your heart out, Paris.?Nina Shapiro