THEY CALL her The Muffin Lady. Every afternoon she treks to a deli on 14th Street to bake. Every morning she wheels her blue cart in front of 1120 20th St., turns on a classical cassette tape and sells breakfast to Washingtonians who have neglected it at home. Faith Collins, Rosalynn Carter's ex-deputy press secretary, has hit the streets.

"Find a better ice cream sandwich and I'll buy it for you," chants the Chips A La Mode man under the umbrella on L Street. A red light changes to green, signaling a new audience of passersby, some of whom are old customers of this vendor, back when the sale was roast beef, and carpet replaced concrete. That was at his father's restaurant. Now Bobby Young, the 33-year-old son of Paul Young, is an ice cream man.

After Saigon fell, egg rolls infiltrated the Mall. Van Vo came to the United States then, and soon purchased a roadway vending truck, one of the many that outline the museums, dispensing hot dogs and egg rolls to hungry tourists. Vo moonlights as an aluminum factory engineer. He used to be a squadron commander in the Vietnamese Air Force.

More diverse than what they sell, food vendors come in all ages and types: the student entrepreneur, the between-city transient, the retired person on a fixed income. And now the ex-professional. Whether it's for a summer job, a supplemental income or a livelihood, according to the health department food vendors are appearing in unusually high numbers this year. With more to come. "People are trying to bring the wolf away from the door," said Grover Tate, supervisor-sanitarian at the District's Environmental Health Department.

Vending has its non-culinary rewards: the building of a reputation as the friendly neighborhood provider; freedom from schedule, at least when the vendor is self-employed; and, if the product catches on, a surprisingly good income. Like any other job, though, it has its headaches. In this case, there are strict health codes to maintain, competitive shop owners to appease, wars between the spaces (fighting with other vendors for choice sidewalk spots) and sometimes patronizing customers.

While her friends are talking about the latest developments in the Falklands, Faith Collins says, she's talking about lugging 20 pounds of bananas. Considered by her regulars as "the best dressed street vendor in Washington" (navy pumps, Izods and hot pink sweaters), Collins admits that she's not a terribly good baker, worries that her muffins aren't big enough and that they don't "bulb out enough."

Nevertheless, her "Briefcase Breakfasts" business sells an average of 175 muffins a morning. Blueberry is the biggest seller, breakfast-less single men are her biggest individual buyers, AT&T is her biggest corporate client and young women are the largest consumers of the nutrient-packed varieties--carrot and bran.

When Collins first started out, she didn't know it was illegal to prepare food in her home (the most common mistake of vendors, according to the health department's Tate). After being buffeted within the bureaucracy, the former White House employe says she doesn't know how some people manage to get vendor licenses. And, she says, "you have to abuse the system in order to make it work for you." For her that means allowing the bananas for her banana nut muffins to ripen at home.

Although Collins does "free-lance consulting" after muffin selling, she doesn't want people to think she's turned to vending because she couldn't get a job. It's not a whimsical endeavor, she says. As she put it, "Right now, I'm just stepping out."

For Bobby Young, the reason he owns Chips A La Mode, one of several competing chocolate chip cookie-ice cream sandwich vending operations that are spilling into the streets, is "because it's fun." But this year, Young's second year on the street, hasn't been that much fun. He has competition, stiff competition. Chipwich.

A New Jersey-based operation that started sales in New York in 1980, Chipwich has been so successful that the corporation plans to vend in 26 cities this summer. In Washington, it has 31 carts. Young has six. The only thing they have in common, contends Young, is the price--$1. As far as the taste, he insists, the sandwiches don't compare. (Joe Wozney, president of the Washington branch of Chipwich A La Carte, of course prefers Chipwich; Chipwich public relations man Michael Orlando says, "Everyone's come out with an imitation of it. That's exactly what they are--imitations.")

Young's cookies are baked in Baltimore, and the ice cream is from a Carvel there. The five-person Chips A La Mode assembly line works like this: One person lays out 60 cookies, behind him another scoops the ice cream onto 30 of them; the next places the other 30 cookies on top, pressing them into sandwiches; the bagger does his thing and the runner dashes them into the freezer. Sounds easy enough, but it gets messy, says Young. The ice cream assembled on the first cookies begins to melt before the runner gets them into the freezer, and the ice cream being scooped from the carton gets soupy, too.

The Chipwich factory in Lodi, New Jersey, capable of making 150,000 cookies a day, works a bit differently. According to assistant plant manager Marion Glasser, this is how its conveyer assembly line works: The cookies arrive from California, where they have been machine-molded. ("For purposes of uniformity and quality control," said Glasser.) Then the ice cream, made from a mix bought locally, goes through a nozzle that spurts out exactly 3 1/2 ounces onto the bottom cookie. The next machine lays on the top cookie, then another presses the top down. Human chip-rollers take over there, rolling the sandwiches in chocolate chips from stainless steel troughs. Everything is temperature-controlled.

Glasser said Chipwich carefully monitors the competition, holding samplings and tastings of its own. And, she said, "we think we make the best."

It's impossible to ignore David Lippmann, a veritable Howard Stern of street vendors. His constant hawking is a comedic routine. He shakes hands, kisses strange cheeks, insults people.

At his regular spot at the entrance to the Foggy Bottom Metro stop, the 23-year-old Corner Gourmet vendor is a hard-sell. Dashing toward the crowd at the stoplight, he shouts, "Do something good for yourself. Let me feed you!" To those exiting the Metro: "People getting off the subway, please consider your gastronomical priorities!"

Lippmann insists that "if you have a product, you promote it." This means convincing passersby that they need a croissant. His tactics work. He sells a lot. Even several ham-and-cheese at 8 a.m.

Corner Gourmet sells about 3,000 croissants a day from 20 carts, croissants that come from a local bakery. Co-owner Nick Tillman is just one of several young businessmen/vending owners who fit the pattern: the just-out-of-school BA's in marketing, the MA's in finance. All about 24 years old. All went to local colleges. One wonders if open-your-own was the final exam.

Today is not a house-selling day for Janie Becker, a 54-year-old real estate agent whose jam cakes are a recent addition to the L Street vending corridor. With straw hat and strawberry smock, Becker looks like a country cook. In a way, she is--Becker also owns Homespun, the jelly and conserve shop on 18th Street. Her jam cakes use surplus orange, lemon or apple marmalade that she sells in her shop, altering a standard applesauce cake recipe for each preserve.

She's had a hard adjustment period on the street. Her age, she feels, inhibits people from approaching her. And, she says, "Vendors are not held in high regard."

So why has she ventured into street vending? Besides taking up the lull before the full-fledged summer fruit season, says Becker, "I'm out here because of Reaganomics."