Over time, the concrete floor will chew up your cleats and shoe heel. At a minimum, get cleat covers. If you prefer road shoes & cleats on the bike, can you carry a pair of slip-ons (like a lot of my kids' baseball/softball/soccer/field hockey/lacrosse-playing friends use when they change out of their cleats) and walk in those? SPD and MTB shoes on a road bike are fine - as long as the cyclist style police, the Velominati (Keepers of the Cog, aka "The Rules"), or NYC Bike Snob arne't around.