When it comes to art collectors in town, there are the Rubells, and then there's everybody else. Martin Margulies has his own minimuseum, so does Ella Fontanals-Cisneros, but the Rubells opened their 5,000-piece collection to the public a decade ago, before any of those amateurs. By choosing Wynwood as their base, they raised the blighted neighborhood's profile, which soon turned into a gallery anthill. And they've also functioned as de facto cheerleaders to the local scene, with their Art Basel breakfasts a must during that annual week of excess. But it's their patronage of local artists such as Purvis Young that have made the native New Yorkers our very own Medicis. Don, a former gynecologist, and Mera, a former Head Start teacher, began collecting art in the '60s, building their collection by spotting unknown artists the way a broker selects stocks with potential. When they came to Miami, they started acquiring our best: Young, Jose Bedia, Bert Rodriguez, and Naomi Fisher are just a few of the names on their walls. Recently, the Rubells bought a $6.5 million property in Washington, D.C., to double as a satellite of their collection. Were they telegraphing moving plans? Mera Rubell would say only: "Nobody should take us for granted."