SoBe is a large area... I'm not sure what you mean by "boardwalk."
Close to Lummus Park (next to the sand) and points South...
Municipal Parking - Parking Garage · 121, 199 13th St (my favorite)
Associated Parking Systems - Parking Lot · 1155 Collins Ave
Public Parking - Parking Lot · 1262 Collins Ave
Pelican Parking Garage - Parking Garage · 1041 Collins Ave
Miami Beach Parking Garage - Parking Garage · 210 7th St
LAZ Parking - Parking Garage · 500 Collins Ave
Central Parking - 555 Washington Ave
The City of Miami Beach has a full list of public places here...
http://web.miamibeachfl.gov/parking/scroll.aspx?id=30958
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