Two ways of getting under the skin of Miami's creative scene: a Vespa tour of off-beat arts venues, and a limo ride around the best MiMo (Miami Modernist) architecture

'Do you guys want soup? It's very good – vegetable. I just finished making it ..." It's not the first thing you expect to hear when meeting a cutting-edge collector of American contemporary art, but there's something maternal and unpretentious about Mera Rubell, co-director of the Rubell Family Collection.

I accept, partly to calm my nerves. I've just ridden here on a Vespa – a cool powder-blue one, no less – with Roam Rides, which offers art tours of Miami by Vespa.

There are numerous art galleries and museums in the city, and 2013 will see the opening of the Miami Art Museum (miamiartmuseum.org), designed by Herzog and de Meuron (of Beijing Olympics fame). Next month it will host the 10th Art Basel Miami Beach (1-4 December, artbasel.com).

The Vespa tour is a brilliant way to explore the city's less obvious art scene. Our guide and instructor for the morning is Kit Sullivan, an amateur artist and graffiti fan who aims to show guests off-the-radar galleries and street art projects. The Rubell rarely appears on tourist maps, has very little marketing and attracts just 200 people a week, but it is a personal collection, where the owners often act as guides.

The building was once a holding facility for the Drug Enforcement Administration (storing tonnes of seized cocaine and cash). It's accessed by a huge, caged doorway. Kit points out bullet holes in the wall.

Mera and her husband Donald began their influential collection in the 1960s. It has now grown to almost 6,500 pieces, with 200 on loan across the world. "We were lucky, I guess," smiles Mera. "We had an eye for it. We bought pieces from Francesco Clemente, Keith Haring, and Jean-Michel Basquiat long before anyone had heard of them."

As we wander round the gallery I'm drawn to some privately commissioned Sterling Ruby canvases. With dark nods to American abstract expressionism, Russian constructivism, graffiti and tribal markings, they're powerful and overwhelming. It's hard to believe the beach is just minutes away.

Then we're on the road again. Riding on Miami's wide open roads is pleasurably sedate, and with the sun on my back I gain confidence and speed. Over the engine noise Kit shouts: "I'm going to take you somewhere we're really proud of in Miami. A few years ago, this area was in decline but wait until you see it. We've got something really cool going on."

Wynwood Walls, a once-derelict warehouse district, is being reborn as an arts neighbourhood. Vast grey walls are being transformed by international street artists including Shepard Fairey (the name behind those iconic 2008 Obama images), Os Gemeos from Brazil, Futura from New York and Lady Aiko of Japan. Musicians, painters, actors and poets are all setting up studios here.

On each corner, a piece of street art is taking shape. The artists don't mind us taking photographs but many refuse to speak to visitors and cover their faces. Hawaiian-born Estria, a pioneer of street art and a respected social historian, is more approachable: "A lot of my friends were b-boys and I used to go watch them breakdancing. I kind of fell into it. With hip-hop arts, it's all connected." 

He's too modest to mention the Estria Foundation (estria.org), set up with Jeremy LaTrasse, co-founder of Twitter. The organisation was conceived to effect "social change through art" by fundraising and art events.

As he paints, he talks me through some terminology. A "bomb" is an illegal work, "thrown up" fast, often at night. "Slashing" (when an artist "throws up" his tag over a legal piece) is one of the most disrespectful things that can happen in graffiti.

On the way back to the hotel I gawp at the stunning art deco facades of Ocean Drive, and am keen to learn more about the city's architecture. So I book a MiMo (Miami Modernist) tour with Charles J Kropke, an architectural historian who has written a book on MiMo (between overseeing 20 companies and his single-parent family of eight adopted kids).

We will be touring the classics of the future, not this time by Vespa, but like rap-stars – in a limousine with drinks cabinet, leather seats, tinted windows and mirrored ceilings.

Our first stop is the International Inn on the Miami Beach side of 79th Street Causeway. In the unrestored 1956 building, Charles leads us to a shimmering pool: "Just look at those blue opaque tiles. I can see this as an incredible boutique hotel – the way those doors all open on to the pool, that crisp, easy symmetry. It's so Miami."

The Formica counter is a little chipped, but I can picture a vacationing Don Draper in the vintage lounge chair, louchely raising a Martini glass through swirls of cigarette smoke.

Down the road is another off-beat jewel, the New Yorker hotel on Biscayne Boulevard, with pastel bath suites and vintage ceiling fans in every room. "The owners spent 18 months sourcing the original-font nameplates for the bedroom doors," says the receptionist.

We take in motels, garages, diners, ice-cream parlours. The tour is so new that one or two of the owners seem pleasantly surprised to see us.

The Biltmore Hotel is not strictly MiMo, but we make an exception. The 1920s Spanish Revivalist resort with its Moorish tower and sweeping driveway oozes Miami glamour. The enormous, U-shaped pool was groundbreaking in its day and hosted beauty pageants and synchronised swimming displays. We learn that Johnny Weissmuller worked here as a lifeguard and had a penchant for streaking on the job.

There's one more building to see – the Pan Am terminal at Dinner Key, one of the earliest international seaplane airports and a reminder of the glamour of the golden years of aviation, portrayed in the new TV series Pan Am, which started on BBC2 this week. The clattering heels have long fallen silent but the magnificent winged clock stands as a timely reminder of one of Miami's brightest eras.

• The Rubell Family Collection's American Exuberance exhibition runs from 30 November until July 2012 (rfc.museum). Street art scooter tours cost $75pp plus $50 for a two-person scooter (+1 888 760 7626, roamrides.com). Charles J Kropke's tailormade architecture tours from $65-$85pp (+1 305 774 9019, dragonflyexpeditions.com). KLM (klm.com) flies Heathrow-Miami from £401 return. The Morgan Mondrian (+1 305 514 1500, mondrian-miami.com), on South Beach has doubles from $270. Doubles at the New Yorker (hotelnewyorkermiami.com) from $125